Factorized Parameter Estimation for Real-Time Gravitational Wave Inference [CL]

http://arxiv.org/abs/2210.16278


We present a parameter estimation framework for gravitational wave (GW) signals that brings together several ideas to accelerate the inference process. First, we use the relative binning algorithm to evaluate the signal-to-noise-ratio timeseries in each detector for a given choice of intrinsic parameters. Second, we decouple the estimation of the intrinsic parameters (such as masses and spins of the components) from that of the extrinsic parameters (such as distance, orientation, and sky location) that describe a binary compact object coalescence. We achieve this by semi-analytically marginalizing the posterior distribution over extrinsic parameters without repeatedly evaluating the waveform for a fixed set of intrinsic parameters. Finally, we augment samples of intrinsic parameters with extrinsic parameters drawn from their appropriate conditional distributions. We implement the method for binaries with aligned spins, restricted to the quadrupole mode of the signal. Using simulated GW signals, we demonstrate that the method produces full eleven-dimensional posteriors that match those from standard Bayesian inference. Our framework takes only ~200 seconds to analyze a typical binary-black-hole signal and ~250 seconds to analyze a typical binary-neutron-star signal using one computing core. Such real-time and accurate estimation of the binary source properties will greatly aid the interpretation of triggers from gravitational wave searches, as well as the search for possible electromagnetic counterparts. We make the framework publicly available via the GW inference package cogwheel.

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T. Islam, J. Roulet and T. Venumadhav
Mon, 31 Oct 22
49/60

Comments: 11 pages, 4 figures

Prospects for Constraining the Yukawa Gravity with Pulsars around Sagittarius A* [HEAP]

http://arxiv.org/abs/2210.16130


The discovery of radio pulsars (PSRs) around the supermassive black hole (SMBH) in our Galactic Center (GC), Sagittarius A* (Sgr A), will have significant implications for tests of gravity. In this paper, we predict restrictions on the parameters of the Yukawa gravity by timing a pulsar around Sgr A with a variety of orbital parameters. Based on a realistic timing accuracy of the times of arrival (TOAs), $\sigma_{\rm TOA}=100\,\mu{\rm s}$, and using a number of 960 TOAs in a 20-yr observation, our numerical simulations show that the PSR-SMBH system will improve current tests of the Yukawa gravity when the range of the Yukawa interaction varies between $10^{1}$-$10^{4}\,{\rm AU}$, and it can limit the graviton mass to be $m_g \lesssim 10^{-24}\,{\rm eV}/c^2$.

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Y. Dong, L. Shao, Z. Hu, et. al.
Mon, 31 Oct 22
50/60

Comments: 17 pages, 5 figures

Extended Tolman III and VII solutions in $f(\mathcal{R},T)$ gravity. I. Models for neutron stars and supermassive stars [CL]

http://arxiv.org/abs/2210.15597


In the context of linear $f(\mathcal{R},T)=\mathcal{R}+\chi T$ gravity, where $\mathcal{R}$ is the Ricci scalar, $T$ is the trace of the energy-momentum tensor, and $\chi$ is a dimensionless parameter, we have obtained exact analytical and numerical solutions for isotropic perfect-fluid spheres in hydrostatic equilibrium. Our solutions correspond to two-parametric extensions of the Tolman III (T-III) and Tolman VII (T-VII) models, in terms of the compactness $\beta$ and $\chi$. By requiring configurations that exhibit monotonically decreasing radial profiles for both the energy density and pressure, compliance with the energy conditions, as well as subluminal speed of sound, we have constrained the parametric space of our solutions. We have also obtained analytically a parametric deformation of the T-VII solution that continuously interpolates between the T-III and T-VII models for any $\chi$, and in the appropriate limits, provides an analytic approximation for the uniform density configuration in linear $f(\mathcal{R},T)$ gravity. Finally, by integrating numerically the TOV equations, we have obtained a numerical solution for the uniform-density configuration and subsequently, using the mass-radius relations, we have obtained the maximum mass that can be supported by such configurations. We have found that in the appropriate parametric regime our solution is in very good agreement with the observational bounds for the masses and radii of neutron stars.

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T. Pappas, C. Posada and Z. Stuchlík
Fri, 28 Oct 22
10/56

Comments: 24 pages, 20 figures, 1 table

Renormalization Group for Non-minimal $φ^2 R$ Couplings and Gravitational Contact Interactions [CL]

http://arxiv.org/abs/2210.15640


Theories of scalars and gravity, with an Einstein-Hilbert term and non-minimal interactions, $M^2R/2 -\alpha\phi^2R/12 $, have graviton exchange induced contact interactions. These modify the renormalization group, leading to a discrepancy between the conventional calculations in the Jordan frame that ignore this effect (and are found to be incorrect), and the Einstein frame in which $\alpha$ does not exist. Thus, the calculation of quantum effects in the Jordan and Einstein frames does not generally commute with the transition from the Jordan to the Einstein frame. In the Einstein frame, though $\alpha$ is absent, for small steps in scale $\delta\mu/\mu$ infinitesimal contact terms $\sim \delta\alpha$ are induced, that are then absorbed back into other couplings by the contact terms. This modifies the $\beta$-functions in the Einstein frame. We show how correct results can be obtained in a simple model by including this effect.

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D. Ghilencea and C. Hill
Fri, 28 Oct 22
18/56

Comments: 11 pages, 4 figures. arXiv admin note: text overlap with arXiv:2009.14782

Construction and evolution of equilibrium configurations of the Schrödinger-Poisson system in the Madelung frame [CL]

http://arxiv.org/abs/2210.15608


We present the construction of ground state equilibrium configurations of the Schr\”odinger-Poisson (SP) system in the Madelung frame and evolve such configuration using finite volume methods. We compare the behavior of these configurations when evolved within the SP and Madelung frames, in terms of conservation of mass and energy. We also discuss the issues of the equations in the Madelung frame and others inherent to the numerical methods used to solve them.

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I. Alvarez-Ríos and F. Guzmán
Fri, 28 Oct 22
19/56

Comments: 12 pages, 4 figures. Invited contribution

Solvable potentials in a FLRW+Scalar universe and Fits to type Ia supernovae data [CL]

http://arxiv.org/abs/2210.15475


FLRW equations are analyzed in a universe with a cosmic scalar background that is spatially uniform but time-varying. Some solvable scalar potentials to the combined dynamics in such a universe are presented. They are consistent with the scalar dynamics as a consequence of energy momentum conservation. Certain potentials are found to provide very good fits to type Ia supernovae data, with the kinetic and potential energies of the scalar providing the source for dark matter and dark energy. The scalar rolls down the potential as the universe expands, with the potential playing the role of a time-varying cosmological constant, modeling a scenario recently discussed in the literature.

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B. Balakrishna
Fri, 28 Oct 22
23/56

Comments: N/A

Missed opportunities: GRB 211211A and the case for continual gravitational-wave coverage with a single observatory [HEAP]

http://arxiv.org/abs/2210.14938


Gamma-ray burst GRB 211211A may have been the result of a neutron star merger at $\approx350$ Mpc. However, none of the LIGO-Virgo detectors were operating at the time. We show that the gravitational-wave signal from a \grb-like binary neutron star inspiral in the next LIGO-Virgo-KAGRA observing run (O4) would be below the conventional detection threshold, however a coincident gamma-ray burst observation would provide necessary information to claim a statistically-significant multimessenger observation. We calculate that with O4 sensitivity, approximately $11\%$ of gamma-ray bursts within 600 Mpc will produce a confident association between the gravitational-wave binary neutron star inspiral signature and the prompt gamma-ray signature. This corresponds to a coincident detection rate of $\unit[0.22^{+8.3}{-0.22}]{yr^{-1}}$, where the uncertainties are the 90\% confidence intervals arising from uncertainties in the absolute merger rate, beaming and jet-launching fractions. These increase to approximately $34\%$ and $\unit[0.71^{+26.8}{-0.70}]{yr^{-1}}$ with proposed O5 sensitivity. We show that the above numbers do not depend significantly on the number of gravitational-wave observatories operating with the specific sensitivity. That is, the number of confident joint gamma-ray burst and gravitational-wave detections is only marginally improved with two or three detectors operating compared to a single detector. It is therefore worth considering whether one detector with sufficient sensitivity (post O4) should remain in sky-watch mode at all times to elucidate the true nature of GRB 211211A-like events, a proposal we discuss in detail.

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N. Sarin, P. Lasky and R. Nathan
Fri, 28 Oct 22
30/56

Comments: Submitted to MNRAS, 7 pages 2 figures

Virgo Detector Characterization and Data Quality: results from the O3 run [CL]

http://arxiv.org/abs/2210.15633


The Advanced Virgo detector has contributed with its data to the rapid growth of the number of detected gravitational-wave (GW) signals in the past few years, alongside the two Advanced LIGO instruments. First during the last month of the Observation Run 2 (O2) in August 2017 (with, most notably, the compact binary mergers GW170814 and GW170817), and then during the full Observation Run 3 (O3): an 11-months data taking period, between April 2019 and March 2020, that led to the addition of about 80 events to the catalog of transient GW sources maintained by LIGO, Virgo and now KAGRA. These discoveries and the manifold exploitation of the detected waveforms require an accurate characterization of the quality of the data, such as continuous study and monitoring of the detector noise sources. These activities, collectively named {\em detector characterization and data quality} or {\em DetChar}, span the whole workflow of the Virgo data, from the instrument front-end hardware to the final analyses. They are described in details in the following article, with a focus on the results achieved by the Virgo DetChar group during the O3 run. Concurrently, a companion article describes the tools that have been used by the Virgo DetChar group to perform this work.

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F. Acernese, M. Agathos, A. Ain, et. al.
Fri, 28 Oct 22
36/56

Comments: 57 pages, 18 figures. To be submitted to Class. and Quantum Grav. This is the “Results” part of preprint arXiv:2205.01555 [gr-qc] which has been split into two companion articles: one about the tools and methods, the other about the analyses of the O3 Virgo data

Virgo Detector Characterization and Data Quality: tools [CL]

http://arxiv.org/abs/2210.15634


Detector characterization and data quality studies — collectively referred to as {\em DetChar} activities in this article — are paramount to the scientific exploitation of the joint dataset collected by the LIGO-Virgo-KAGRA global network of ground-based gravitational-wave (GW) detectors. They take place during each phase of the operation of the instruments (upgrade, tuning and optimization, data taking), are required at all steps of the dataflow (from data acquisition to the final list of GW events) and operate at various latencies (from near real-time to vet the public alerts to offline analyses). This work requires a wide set of tools which have been developed over the years to fulfill the requirements of the various DetChar studies: data access and bookkeeping; global monitoring of the instruments and of the different steps of the data processing; studies of the global properties of the noise at the detector outputs; identification and follow-up of noise peculiar features (whether they be transient or continuously present in the data); quick processing of the public alerts. The present article reviews all the tools used by the Virgo DetChar group during the third LIGO-Virgo Observation Run (O3, from April 2019 to March 2020), mainly to analyse the Virgo data acquired at EGO. Concurrently, a companion article focuses on the results achieved by the DetChar group during the O3 run using these tools.

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F. Acernese, M. Agathos, A. Ain, et. al.
Fri, 28 Oct 22
52/56

Comments: 44 pages, 16 figures. To be submitted to Class. and Quantum Grav. This is the “Tools” part of preprint arXiv:2205.01555 [gr-qc] which has been split into two companion articles: one about the tools and methods, the other about the analyses of the O3 Virgo data

Joint photon-electron Lorentz violation parameter plane from LHAASO data [HEAP]

http://arxiv.org/abs/2210.14817


The Large High Altitude Air Shower Observatory~(LHAASO) is one of the most sensitive gamma-ray detector arrays, whose ultrahigh-energy~(UHE) work bands not only help to study the origin and acceleration mechanism of UHE cosmic rays, but also provide the opportunity to test fundamental physics concepts such as Lorentz symmetry. LHAASO directly observes the $1.42~\mathrm{PeV}$ highest-energy photon. By adopting the synchrotion self-Compton model LHAASO also suggests that the $1.12~\mathrm{PeV}$ high-energy photon from Crab Nebula corresponds to a $2.3~\mathrm{PeV}$ high-energy electron. We study the $1.42~\mathrm{PeV}$ photon decay and the $2.3~\mathrm{PeV}$ electron decay to perform a joint analysis on photon and electron two-dimensional Lorentz violation~(LV) parameter plane. Our analysis is systematic and comprehensive, and we naturally get the strictest constraints from merely considering photon LV effect in photon decay and electron LV effect in electron decay. Our result also permits the parameter space for new physics beyond relativity.

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P. He and B. Ma
Thu, 27 Oct 22
23/55

Comments: 8 latex pages, 3 figures, version for journal publication

Redshift-evolutionary X-ray and UV luminosity relation of quasars from Gaussian copula [CEA]

http://arxiv.org/abs/2210.14432


We construct a three-dimensional and redshift-evolutionary X-ray and ultraviolet ($L_X-L_{UV}$) luminosity relation for quasars from the powerful statistic tool called copula, and find that the constructed $L_X-L_{UV}$ relation from copula is more viable than the standard one and the observations favor the redshift-evolutionary relation more than $3\sigma$. The Akaike and Bayes information criterions indicate that the quasar data support strongly the three-dimensional $L_X-L_{UV}$ relation. Our results show that the quasars can be regarded as a reliable indicator of the cosmic distance if the $L_X-L_{UV}$ relation from copula is used to calibrate quasar data.

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B. Wang, Y. Liu, Z. Yuan, et. al.
Thu, 27 Oct 22
26/55

Comments: 15 pages, 6 figures. Accepted for publication in ApJ

Spherical collapse of non-top-hat profiles in the presence of dark energy with arbitrary sound speed [CEA]

http://arxiv.org/abs/2210.14769


We study the spherical collapse of non-top-hat matter fluctuations in the presence of dark energy with arbitrary sound speed. The model is described by a system of partial differential equations solved using a pseudo-spectral method with collocation points. This method can reproduce the known analytical solutions in the linear regime with an accuracy better than $10^{-6}\%$ and better than $10^{-2}\%$ for the virialization threshold given by the usual spherical collapse model. We show the impact of nonlinear dark energy fluctuations on matter profiles, matter peculiar velocity and gravitational potential. We also show that phantom dark energy models with low sound speed can develop a pathological behaviour around matter halos, namely negative energy density. The dependence of the virialization threshold density for collapse on the dark energy sound speed is also computed, confirming and extending previous results in the limit for homogeneous and clustering dark energy.

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R. Batista, H. Oliveira and L. Abramo
Thu, 27 Oct 22
31/55

Comments: 22 pages, 12 figures

Quasinormal modes in higher derivative gravity: testing the black hole parametrization and sensitivity of overtones [CL]

http://arxiv.org/abs/2210.14506


The fundamental quasinormal modes of black holes in higher derivative gravity given by the Einstein-Weyl action are known to be moderately corrected by the Weyl term. Here we will show that the first several overtones are highly sensitive to even a relatively small Weyl correction, which might be important when representing the earlier stage of the black-hole ringdown. In addition, we have solved the problem related to analytical parametrized approximation of the numerical black hole solution in the Einstein-Weyl theory: In some range of parameters the approximation for the metric developed up to the third order lead to the unusual highly non-monotonic behavior of the frequencies. We have shown that this problem can be solved via the extension of the parametrization of the metric to higher orders until reaching the regime when the frequencies do not change with further increasing of the order.

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R. Konoplya
Thu, 27 Oct 22
40/55

Comments: 7 pages, 3 figures, 2 tables, revtex

Search for gravitational-wave transients associated with magnetar bursts during the third Advanced LIGO and Advanced Virgo observing run [HEAP]

http://arxiv.org/abs/2210.14258


Magnetars are neutron stars with exceptionally strong dipole magnetic fields which are observed to display a range of x-ray flaring behavior, but the flaring mechanism is not well understood. The third observing run of Advanced LIGO and Virgo extended from April 1, 2019 to March 27, 2020, and contained x-ray flares from known magnetar SGR 1935+2154, as well as the newly-discovered magnetar, Swift J1818-1607. We search for gravitational waves coincident with these magnetar flares with minimally modeled, coherent searches which specifically target both short-duration gravitational waves produced by excited f-modes in the magnetar’s core, as well as long-duration gravitational waves motivated by the Quasi-Periodic Oscillations observed in the tails of giant flares. In this paper, we report on the methods and sensitivity estimates of these searches, and the astrophysical implications.

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K. Merfeld
Thu, 27 Oct 22
53/55

Comments: N/A

Measuring Photon Rings with the ngEHT [HEAP]

http://arxiv.org/abs/2210.13498


General relativity predicts that images of optically thin accretion flows around black holes should generically have a photon ring,'' composed of a series of increasingly sharp subrings that correspond to increasingly strongly lensed emission near the black hole. Because the effects of lensing are determined by the spacetime curvature, the photon ring provides a pathway to precise measurements of the black hole properties and tests of the Kerr metric. We explore the prospects for detecting and measuring the photon ring using very long baseline interferometry (VLBI) with the Event Horizon Telescope (EHT) and the next generation EHT (ngEHT). We present a series of tests using idealized self-fits to simple geometrical models and show that the EHT observations in 2017 and 2022 lack the angular resolution and sensitivity to detect the photon ring, while the improved coverage and angular resolution of ngEHT at 230 GHz and 345 GHz is sufficient for these models. We then analyze detection prospects using more realistic images from general relativistic magnetohydrodynamic simulations by applyinghybrid imaging,” which simultaneously models two components: a flexible raster image (to capture the direct emission) and a ring component. Using the Bayesian VLBI modeling package \comrade, we show that the results of hybrid imaging must be interpreted with extreme caution for both photon ring detection and measurement — hybrid imaging readily produces false positives for a photon ring, and its ring measurements do not directly correspond to the properties of the photon ring.

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P. Tiede, M. Johnson, D. Pesce, et. al.
Wed, 26 Oct 22
4/73

Comments: submission to ngEHT galaxy special issue

Effective two-body approach to the hierarchical three-body problem: quadrupole to 1PN [CL]

http://arxiv.org/abs/2210.13493


Many binary systems of interest for gravitational-wave astronomy are orbited by a third distant body, which can considerably alter their relativistic dynamics. Precision computations are needed to understand the interplay between relativistic corrections and three-body interactions. We use an effective field theory approach to derive the effective action describing the long time-scale dynamics of hierarchical three-body systems up to 1PN quadrupole order. At this level of approximation, computations are complicated by the backreaction of small oscillations on orbital time-scales as well as deviations from the adiabatic approximation. We address these difficulties by eliminating the fast modes through the method of near-identity transformations. This allows us to compute for the first time the complete expression of the 1PN quadrupole cross-terms in generic configurations of three-body systems. We numerically integrate the resulting equations of motion and show that 1PN quadrupole terms can affect the long term dynamics of relativistic three-body systems.

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A. Kuntz, F. Serra and E. Trincherini
Wed, 26 Oct 22
6/73

Comments: 41 pages, 3 figures

Similar general relativistic magnetohydrodynamic codes produce different results for binary neutron star mergers [CL]

http://arxiv.org/abs/2210.13481


In this paper, we show that similar open-source codes for general relativistic magnetohydrodynamic (GRMHD) produce different results for key features of binary neutron star mergers. First, we present a new open-source version of the publicly available IllinoisGRMHD code that provides support for realistic, finite temperature equations of state. After stringent tests of our upgraded code, we perform a code comparison between GRHydro, IllinoisGRMHD, Spritz, and WhiskyTHC, which implement the same physics, but slightly different computational methods. The benefit of the comparison is that all codes are embedded in the EinsteinToolkit suite, hence their only difference is algorithmic. We find similar convergence properties, fluid dynamics, and gravitational waves, but different merger times, remnant lifetimes, and gravitational wave phases. Such differences must be resolved before the post-merger dynamics modeled with such simulations can be reliably used to infer the properties of nuclear matter especially in the era of precision gravitational wave astronomy.

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P. Espino, G. Bozzola and V. Paschalidis
Wed, 26 Oct 22
19/73

Comments: N/A

Dynamical analysis of the redshift drift in FLRW universes [CL]

http://arxiv.org/abs/2210.13946


Redshift drift is the phenomenon whereby the observed redshift between an emitter and observer comoving with the Hubble flow in an expanding FLRW universe will slowly evolve — on a timescale comparable to the Hubble time. In a previous article [JCAP 04 (2020) 043; \arXiv{2001.11964}] three of the current authors had performed a cosmographic analysis of the redshift drift in a FLRW universe, temporarily putting aside the issue of dynamics (the Friedmann equations). In the current article we now add dynamics, still within the framework of an exact FLRW universe. We shall develop a suitable generic matter model, and study both the low-redshift asymptotic behaviour and the utility of using alternative variables to describe the redshift.

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F. Lobo, J. Mimoso, J. Santiago, et. al.
Wed, 26 Oct 22
22/73

Comments: 34 pages, 4 figures

Crustal failure as a tool to probe hybrid stars [HEAP]

http://arxiv.org/abs/2210.14048


It is currently unknown if neutron stars are composed of nucleons only or are hybrid stars, i.e., in addition to nucleonic crusts and outer cores, they also possess quark cores. Quantum chromodynamics allows for such a phase transition possibility, but accurate calculations in the range of interest for compact stars are still elusive. Here we investigate some crust-breaking aspects of hybrid stars. We show that the crust-breaking orbital/gravitational wave frequency and maximum ellipticity are sensitive to the quark-hadron density jump and equation of state stiffness. Remarkably, the crust-breaking frequency related to static tides scales linearly with the mass of the star (for a given companion’s mass), and its slope encompasses information about the microphysics of the star. When a liquid quark core touches an elastic hadronic phase, which could be the result of a significant energy-density jump, the maximum ellipticity can increase orders of magnitude when compared to the case the liquid quark core touches a liquid hadronic phase, such as the outer core. Our analysis also suggests that a given upper limit to the ellipticity or a crust-breaking frequency could have representatives in stars with either small or very large energy-density jumps. Therefore, upper limits to the ellipticity from continuous gravitational wave observations of the LIGO-Virgo-KAGRA network for isolated stars, and gamma-ray precursors associated with crust breaking in inspiraling binary systems may constrain some aspects of phase transitions in neutron stars.

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J. Pereira, M. Bejger, P. Haensel, et. al.
Wed, 26 Oct 22
27/73

Comments: 10 pages, 6 figures. Comments welcome

Gravitational Waves and Primordial Black Hole Productions from Gluodynamics [CL]

http://arxiv.org/abs/2210.14094


We construct a holographic model describing the gluon sector of Yang-Mills theories at finite temperature in the non-perturbative regime. The equation of state as a function of temperature is in good accordance with the lattice quantum chromodynamics (QCD) data. Moreover, the Polyakov loop and the gluon condensation, which are proper order parameters to capture the deconfinement phase transition, also agree quantitatively well with the lattice QCD data. We obtain a strong first-order confinement/deconfinement phase transition at $T_c=276.5\,\text{MeV}$ that is consistent with the lattice QCD prediction. The resulting stochastic gravitational-wave backgrounds from this confinement/deconfinement phase transition are obtained with potential detectability in the International Pulsar Timing Array and Square Kilometre Array in the near future when the associated productions of primordial black holes (PBHs) saturate the current observational bounds on the PBH abundances from the LIGO-Virgo-Collaboration O3 data.

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S. He, L. Li, Z. Li, et. al.
Wed, 26 Oct 22
33/73

Comments: 5 pages + appendix, 5 figures

Asymmetrical tidal tails of open star clusters: stars crossing their cluster's prah challenge Newtonian gravitation [GA]

http://arxiv.org/abs/2210.13472


After their birth a significant fraction of all stars pass through the tidal threshold (prah) of their cluster of origin into the classical tidal tails. The asymmetry between the number of stars in the leading and trailing tails tests gravitational theory. All five open clusters with tail data (Hyades, Praesepe, Coma Berenices, COIN-Gaia 13, NGC 752) have visibly more stars within dcl = 50 pc of their centre in their leading than their trailing tail. Using the Jerabkova-compact-convergent-point (CCP) method, the extended tails have been mapped out for four nearby 600-2000 Myr old open clusters to dcl>50 pc. These are on near-circular Galactocentric orbits, a formula for estimating the orbital eccentricity of an open cluster being derived. Applying the Phantom of Ramses code to this problem, in Newtonian gravitation the tails are near-symmetrical. In Milgromian dynamics (MOND) the asymmetry reaches the observed values for 50 < dcl/pc < 200, being maximal near peri-galacticon, and can slightly invert near apo-galacticon, and the K\”upper epicyclic overdensities are asymmetrically spaced. Clusters on circular orbits develop orbital eccentricity due to the asymmetrical spill-out, therewith spinning up opposite to their orbital angular momentum. This positive dynamical feedback suggests Milgromian open clusters to demise rapidly as their orbital eccentricity keeps increasing. Future work is necessary to better delineate the tidal tails around open clusters of different ages and to develop a Milgromian direct n-body code.

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P. Kroupa, T. Jerabkova, I. Thies, et. al.
Wed, 26 Oct 22
38/73

Comments: 28 pages, 19 figures, MNRAS, published

Clusteringenesis: from Light to Heavy Primordial Black Holes [CEA]

http://arxiv.org/abs/2210.14171


We show that heavy primordial black holes may originate from much lighter ones if the latter are strongly clustered at the time of their formation. While this population is subject to the usual constraints from late-time universe observations, its relation to the initial conditions is different from the standard scenario and provides a new mechanism to generate massive primordial black holes even in the absence of efficient accretion, opening new scenarios, e.g. for the generation of supermassive black holes.

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V. Luca, G. Franciolini and A. Riotto
Wed, 26 Oct 22
45/73

Comments: 5 pages, 2 figures

Inflation from Multiple Pseudo-Scalar Fields: PBH Dark Matter and Gravitational Waves [CEA]

http://arxiv.org/abs/2210.13822


We study a model of inflation with multiple pseudo-scalar fields coupled to a $U(1)$ gauge field through Chern-Simons interactions. Because of parity violating interactions, one polarization of the gauge field is amplified yielding to enhanced curvature perturbation power spectrum. Inflation proceeds in multiple stages as each pseudo-scalar field rolls towards its minimum yielding to distinct multiple peaks in the curvature perturbations power spectrum at various scales during inflation. The localized peaks in power spectrum generate Primordial Black Holes (PBHs) which can furnish a large fraction of Dark Matter (DM) abundance. In addition, gravitational waves (GWs) with non-trivial spectra are generated which are in sensitivity range of various forthcoming GW observatories.

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A. Talebian, S. Mansoori and H. Firouzjahi
Wed, 26 Oct 22
47/73

Comments: This work is dedicated to the memory of Prof. Mohammad Reza Setare (1974-2022)

Slowly Decaying Ringdown of a Rapidly Spinning Black Hole: Probing the No-Hair Theorem by Small Mass-Ratio Mergers with LISA [CL]

http://arxiv.org/abs/2210.14049


The detectability of multiple quasi-normal (QN) modes, including overtones and higher harmonics, with the Laser Interferometer Space Antenna (LISA) is investigated by computing the gravitational wave (GW) signal induced by an intermediate or extreme mass ratio merger involving a supermassive black hole (SMBH). We confirm that the ringdown of rapidly spinning black holes are long-lived, and higher harmonics of the ringdown are significantly excited for mergers of small mass ratios. We demonstrate that the observation of GWs from rapidly rotating SMBHs has a significant advantage for detecting multiple QN modes and testing the no-hair theorem of black holes with high accuracy.

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N. Oshita and D. Tsuna
Wed, 26 Oct 22
49/73

Comments: 6 pages, 6 figures

Tidal Deformability of Neutron Stars in Scalar-Tensor Theories of Gravity for Gravitational Wave Analysis [CL]

http://arxiv.org/abs/2210.14025


Gravitational waves from compact binary coalescence are valuable for testing theories of gravity in the strong field regime. By measuring neutron star tidal deformability in gravitational waves from binary neutron stars, stringent constraints were placed on the equation of state of matter at extreme densities. Tidal Love numbers in alternative theories of gravity may differ significantly from their general relativistic counterparts. Understanding exactly how the tidal Love numbers change will enable scientists to untangle effects from physics beyond general relativity from the uncertainty in the equation of state measurement. In this work, we explicitly calculate the fully relativistic $l \geq 2$ tidal love numbers for neutron stars in scalar-tensor theories of gravitation. We use several realistic equations of state to explore how the mass, radius, and tidal deformability relations differ from those of general relativity. We find that tidal Love numbers and tidal deformabilities can differ significantly from those in general relativity ( $>200\%$ in strong scalarization cases) in certain regimes. This difference suggests that using the tidal Love numbers from general relativity could lead to significant errors in tests of general relativity using the gravitational waves from binary neutron star and neutron star-black hole mergers.

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S. Brown
Wed, 26 Oct 22
50/73

Comments: Planned for submission to APJ

Exotic Compact Objects with Two Dark Matter Fluids [CL]

http://arxiv.org/abs/2210.13697


The generic properties of compact objects made of two different fluids of dark matter are studied in a scale invariant approach. We investigate compact objects with a core-shell structure, where the two fluids are separated, and with mixed dark matter components, where both dark matter fluids are immersed within each other. The constellations considered are combinations of incompressible fluids, free and interacting Fermi gases, and equations of state with a vacuum term, i.e. self-bound dark matter. We find novel features in the mass-radius relations for combined dark matter compact objects which distinguishes them from compact objects with a single dark matter fluid and compact stars made of ordinary baryonic matter, as white dwarfs, neutron stars and quark stars. The maximum compactness of certain combined dark matter stars can reach values up to the causality limit for compact stars but not beyond that limit if causality of the dark matter fluids is ensured.

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M. Cassing, A. Brisebois, M. Azeem, et. al.
Wed, 26 Oct 22
64/73

Comments: 11 pages, 13 figures

On the Merger Rate of Primordial Black Holes in Cosmic Voids [CEA]

http://arxiv.org/abs/2210.13558


Cosmic voids are known as underdense substructures of the cosmic web that cover a large volume of the Universe. It is known that cosmic voids contain a small number of dark matter halos, so the existence of primordial black holes (PBHs) in these secluded regions of the Universe is not unlikely. In this work, we calculate the merger rate of PBHs in dark matter halos structured in cosmic voids and determine their contribution to gravitational wave events resulting from black hole mergers recorded by the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO)-Advanced Virgo (aVirgo) detectors. Relying on the PBH scenario, the results of our analysis indicate that about $2 \sim 3$ annual events of binary black hole mergers out of all those recorded by the aLIGO-aVirgo detectors should belong to cosmic voids. We also calculate the redshift evolution of the merger rate of PBHs in cosmic voids. The results show that the evolution of the merger rate of PBHs has minimum sensitivity to the redshift changes, which seems reasonable while considering the evolution of cosmic voids. Finally, we specify the behavior of the merger rate of PBHs as a function of their mass and fraction in cosmic voids and we estimate $\mathcal{R} (M_{PBH}, f_{PBH})$ relation, which is well compatible with our findings.

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S. Fakhry, S. Tabasi and J. Firouzjaee
Wed, 26 Oct 22
72/73

Comments: 10 pages; 4 figures; References are included

Cosmological Information in Skew Spectra of Biased Tracers in Redshift Space [CEA]

http://arxiv.org/abs/2210.12743


Extracting the non-Gaussian information encoded in the higher-order clustering statistics of the large-scale structure is key to fully realizing the potential of upcoming galaxy surveys. We investigate the information content of the redshift-space {\it weighted skew spectra} of biased tracers as efficient estimators for 3-point clustering statistics. The skew spectra are constructed by correlating the observed galaxy field with an appropriately-weighted square of it. We perform numerical Fisher forecasts using two synthetic datasets; the halo catalogs from the Quijote N-body simulations and the galaxy catalogs from the Molino suite. The latter serves to understand the effect of marginalization over a more complex matter-tracer biasing relation. Compared to the power spectrum multipoles, we show that the skew spectra substantially improve the constraints on six parameters of the $\nu\Lambda$CDM model, ${\Omega_m, \Omega_b, h, n_s, \sigma_8, M_\nu}$. Imposing a small-scale cutoff of $k_{\rm max}=0.25 \, {\rm Mpc}^{-1}h$, the improvements from skew spectra alone range from 23% to 62% for the Quijote halos and from 32% to 71% for the Molino galaxies. Compared to the previous analysis of the bispectrum monopole on the same data and using the same range of scales, the skew spectra of Quijote halos provide competitive constraints. Conversely, the skew spectra outperform the bispectrum monopole for all cosmological parameters for the Molino catalogs. This may result from additional anisotropic information, particularly enhanced in the Molino sample, that is captured by the skew spectra but not by the bispectrum monopole. Our stability analysis of the numerical derivatives shows comparable convergence rates for the power spectrum and the skew spectra, indicating potential underestimation of parameter uncertainties by at most 30%.

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J. Hou, A. Dizgah, C. Hahn, et. al.
Tue, 25 Oct 22
26/111

Comments: 43 pages, 25 figures

Enhanced power of gravitational waves and rapid coalescence of black hole binaries through dark energy accretion [CL]

http://arxiv.org/abs/2210.12502


We consider the accretion of dark energy by constituent black holes in binary formations during the present epoch of the Universe. In the context of an observationally consistent dark energy model, we evaluate the growth of black holes’ masses due to accretion. We show that accretion leads to faster circularization of the binary orbits. We compute the average power of the gravitational waves emitted from binaries, which exhibits a considerable enhancement due to the effect of growth of masses as a result of accretion. This in turn, leads to a significant reduction of the coalescence time of the binaries. We present examples pertaining to various choices of the initial masses of the black holes in the stellar mass range and above, in order to clearly establish a possible observational signature of dark energy in the emerging era of gravitational wave astronomy.

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A. Sarkar, A. Ali, K. Nayak, et. al.
Tue, 25 Oct 22
27/111

Comments: 9 pages, 6 figures, 1 Table

Testing gravity with gravitational wave friction and gravitational slip [CEA]

http://arxiv.org/abs/2210.12174


Gravitational waves (GWs) emitted by binary sources are interesting signals for testing gravity on cosmological scales since they allow measurements of the luminosity distance. When followed by electromagnetic counterparts, in particular, they enable a reconstruction of the GW-distance-redshift relation. In the context of several modified gravity (MG) theories, even when requiring that the speed of propagation is equal to that of light, this GW distance differs from the standard electromagnetic luminosity distance due to the presence of a modified friction in the GW propagation. The very same source of this friction, which is the running of an effective Planck mass, also affects the scalar sector generating gravitational slip, i.e. a difference between the scalar potentials, an observable that can be inferred from large-scale structure (LSS) probes. In this work, we use Horndeski MG to exemplify precisely the fact that, at the linear perturbation level, parametrizing a single function is enough to describe the simultaneous deviations in the GW distance and the slip. By simulating multimessenger GW events that might be detected by the Einstein Telescope in the future, we compare the constraining power of the two observables on this single degree of freedom. We then combine forecasts of an $\textit{Euclid}$-like survey with GW simulations, coming to the conclusion that, when using $\textit{Planck}$ data to better constrain the cosmological parameters, those future data on the scalar and tensor sectors are competitive to probe such deviations from General Relativity, with LSS giving stronger (but more model-dependent) results than GWs.

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I. Matos, E. Bellini, M. Calvão, et. al.
Tue, 25 Oct 22
49/111

Comments: 26 pages, 10 figures, 4 tables, 1 appendix

Axion-photon conversion of LHAASO multi-TeV and PeV photons [CL]

http://arxiv.org/abs/2210.13120


The Large High Altitude Air Shower Observatory (LHAASO) has reported the detection of a large number of multi-TeV-scale photon events including also several PeV-scale gamma-ray-photon events with energy as high as 1.4~PeV. The possibility that some of these events may have extragalactic origins is not yet excluded. Here we propose a mechanism for the traveling of very-high-energy (VHE) and ultra-high-energy (UHE) photons based upon the axion-photon conversion scenario, which allows extragalactic above-threshold photons to be detected by observers on the Earth. We show that the axion-photon conversation can serve as an alternative mechanism for the very-high-energy features of the newly observed gamma ray burst GRB 221009A.

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G. Zhang and B. Ma
Tue, 25 Oct 22
53/111

Comments: 5 latex pages, 1 figure

A Black-Hole Excision Scheme for General Relativistic Core-Collapse Supernova Simulations [HEAP]

http://arxiv.org/abs/2210.12939


Fallback supernovae and the collapsar scenario for long-gamma ray burst and hypernovae have received considerable interest as pathways to black-hole formation and extreme transient events. Consistent simulations of these scenarios require a general relativistic treatment and need to deal appropriately with the formation of a singularity. Free evolution schemes for the Einstein equations can handle the formation of black holes by means of excision or puncture schemes. However, in constrained schemes, which offer distinct advantages in long-term numerical stability in stellar collapse simulations over well above $10^{4}$ light-crossing time scales, the dynamical treatment of black-hole spacetimes is more challenging. Building on previous work on excision in conformally flat spacetimes, we here present the implementation of a black-hole excision scheme for supernova simulations with the CoCoNuT-FMT neutrino transport code. We describe in detail a choice of boundary conditions that ensures long-time numerical stability, and also address upgrades to the hydrodynamics solver that are required to stably evolve the relativistic accretion flow onto the black hole. The scheme is currently limited to a spherically symmetric metric, but the hydrodynamics can be treated multi-dimensionally. For demonstration, we present a spherically symmetric simulation of black-hole formation in an $85 M_\odot$ star, as well as a two-dimensional simulation of the fallback explosion of the same progenitor. These extend past 9s and 0.3s after black-hole formation, respectively.

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B. Sykes, B. Mueller, I. Cordero-Carrión, et. al.
Tue, 25 Oct 22
57/111

Comments: 19 pages, 12 figures. Submitted to PRD

Cosmological consequences of first-order general-relativistic viscous fluid dynamics [CL]

http://arxiv.org/abs/2210.13372


We investigate the out-of-equilibrium dynamics of viscous fluids in a spatially flat Friedmann-Lema\^itre-Robertson-Walker cosmology using the most general causal and stable viscous energy-momentum tensor defined at first order in spacetime derivatives. In this new framework a pressureless viscous fluid having density $\rho$ can evolve to an asymptotic future solution in which the Hubble parameter approaches a constant while $\rho \rightarrow 0$, even in the absence of a cosmological constant (i.e., $\Lambda = 0$). Thus, while viscous effects in this model drive an accelerated expansion of the universe, the density of the viscous component itself vanishes, leaving behind only the acceleration. This behavior emerges as a consequence of causality in first-order theories of relativistic fluid dynamics and it is fully consistent with Einstein’s equations.

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F. Bemfica, M. Disconzi, J. Noronha, et. al.
Tue, 25 Oct 22
85/111

Comments: 14 pages, no figures

Searching for structure in the binary black hole spin distribution [HEAP]

http://arxiv.org/abs/2210.12287


The spins of black holes in merging binaries can reveal information related to the formation and evolution of these systems. Combining events to infer the astrophysical distribution of black hole spins allows us to determine the relative contribution from different formation scenarios to the population. Many previous works have modeled spin population distributions using parametric models. While these are valuable approaches when the observed population is small, they make strong assumptions about the shape of the underlying distribution and are highly susceptible to biases due to mismodeling. The results obtained with such parametric models are only valid if the allowed shape of the distribution is well-motivated (i.e. for astrophysical reasons). In this work, we relax these prior assumptions and model the spin distributions using a more data-driven approach, modeling these distributions with flexible cubic spline interpolants in order to allow for capturing structures that the parametric models cannot. We find that adding this flexibility to the model substantially increases the uncertainty in the inferred distributions, but find a general trend for lower support at high spin magnitude and a spin tilt distribution consistent with isotropic orientations. We infer that 62 – 87% of black holes have spin magnitudes less than a = 0.5, and 27- 50% of black holes exhibit negative $\chi_{\rm eff}$. Using the inferred $\chi_{\rm eff}$ distribution, we place a conservative upper limit of 37% for the contribution of hierarchical mergers to the astrophysical BBH population. Additionally, we find that artifacts from unconverged Monte Carlo integrals in the likelihood can manifest as spurious peaks and structures in inferred distributions, mandating the use of a sufficient number of samples when using Monte Carlo integration for population inference.

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J. Golomb and C. Talbot
Tue, 25 Oct 22
109/111

Comments: 13 pages, 11 figures

Properties of scalar wave emission in a scalar-tensor theory with kinetic screening [CL]

http://arxiv.org/abs/2210.12139


We study numerically the scalar wave emission by a non-spherical oscillation of neutron stars in a scalar-tensor theory of gravity with kinetic screening, considering both the monopole and quadrupole mode emission. In agreement with previous results in the literature, we find that the monopole is always suppressed by the screening effect, regardless of the size of the screening radius, $r_{\rm sc}$. For the quadrupole mode, however, our analysis shows that the suppression only occurs for screening radius larger than the wavelength of scalar waves, $\lambda_{\rm wave}$, but not for $r_{\rm sc} < \lambda_{\rm wave}$. This demonstrates that to fully understand the nature of this theory, it is necessary to study other more complex systems, such as neutron star binaries, considering a wide range of $r_{\rm sc}$ values.

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M. Shibata and D. Traykova
Mon, 24 Oct 22
5/56

Comments: 12 pages, 8 figures; comments welcome!

Forecasting constraints on deviations from general relativity in $f(Q)$ gravity with standard sirens [CL]

http://arxiv.org/abs/2210.11935


In this work, we explore how modified gravity theories based on the non-metricity scalar, known as $f(Q)$ gravity, affects the propagation of gravitational waves from inspiraling of binary systems. We discuss forecast constraints on $f(Q)$ gravity by considering standard siren events in two contexts: i) simulated sources of gravitational waves as black hole – neutron star binary systems, emitting in the frequency band of the third-generation detector represented by the Einstein Telescope (ET); ii) three standard siren mock catalogs based on the merger of massive black hole binaries that are expected to be observed in the operating frequency band of the Laser Interferometer Space Antenna (LISA). We find that, within the ET sensitivity, it will be possible to test deviations from general relativity at $<3\%$ accuracy in the redshift range $0<z<4$, while the main free parameter of the theory is globally constrained at 1.6\% accuracy within the same range. In light of LISA’s forecasts, in the best scenario, we find that the main free parameter of the theory will be constrained at 1.6\% accuracy up to high redshifts. Therefore, we conclude that future gravitational wave observations by ET and LISA will provide a unique way to test, with good accuracy, the nature of gravity up to very large cosmic distances.

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R. D’Agostino and R. Nunes
Mon, 24 Oct 22
40/56

Comments: 11 pages, 3 figures

Model exploration in gravitational-wave astronomy with the maximum population likelihood [IMA]

http://arxiv.org/abs/2210.11641


Hierarchical Bayesian inference is an essential tool for studying the population properties of compact binaries with gravitational waves. The basic premise is to infer the unknown prior distribution of binary black hole and/or neutron star parameters such component masses, spin vectors, and redshift. These distributions shed light on the fate of massive stars, how and where binaries are assembled, and the evolution of the Universe over cosmic time. Hierarchical analyses model the binary black hole population using a prior distribution conditioned on hyper-parameters, which are inferred from the data. However, a misspecified model can lead to faulty astrophysical inferences. In this paper we answer the question: given some data, which prior distribution — from the set of all possible prior distributions — produces the largest possible population likelihood? This distribution (which is not a true prior) is $\pistroke$ (pronounced pi stroke''), and the associated \textit{maximum population likelihood} is $\Lstroke$ (pronouncedL stroke”). We postulate that the structure of $\pistroke$ is a linear superposition of delta functions. We show how $\pistroke$ and $\Lstroke$ can be used for model exploration/criticism. We apply this $\Lstroke$ formalism to study the population of binary black hole mergers observed in LIGO–Virgo–KAGRA’s third Gravitational-Wave Transient Catalog. Based on our results, we discuss possible improvements for gravitational-wave population models.

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E. Payne and E. Thrane
Mon, 24 Oct 22
42/56

Comments: 13 pages, 5 figures

Optimisation of the SVOM satellite strategy for the follow-up of Gravitational wave events [IMA]

http://arxiv.org/abs/2210.12120


The SVOM satellite, to be launched at the end of 2023, is primarily devoted to the multi-wavelength observation of gamma-ray bursts and other higher-energy transients. Thanks to its onboard Microchannel X-ray Telescope and Visible-band Telescope, it is also very well adapted to the electromagnetic follow-up of gravitational wave events. We discuss the SVOM follow-up strategy for gravitational wave trigger candidates provided by LIGO-Virgo-KAGRA. In particular, we make use of recent developments of galaxy catalogs adapted to the horizon of gravitational wave detectors to optimise the chance of counterpart discovery. We also take into account constraints specific to the SVOM platform. Finally, we implement the production of the SVOM observation plan following a gravitational wave alert and quantify the efficiency of several optimisations introduced in this work.

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J. Ducoin, B. Desoubrie, F. Daigne, et. al.
Mon, 24 Oct 22
46/56

Comments: N/A

Binary neutron star merger simulations with neutrino transport and turbulent viscosity: impact of different schemes and grid resolution [HEAP]

http://arxiv.org/abs/2210.11491


We present a systematic numerical relativity study of the impact of different treatment of microphysics and grid resolution in binary neutron star mergers. We consider series of simulations at multiple resolutions comparing hydrodynamics, neutrino leakage scheme, leakage augmented with the M0 scheme and the more consistent M1 transport scheme. Additionally, we consider the impact of a sub-grid scheme for turbulent viscosity. We find that viscosity helps to stabilise the remnant against gravitational collapse but grid resolution has a larger impact than microphysics on the remnant’s stability. The gravitational wave (GW) energy correlates with the maximum remnant density, that can be thus inferred from GW observations. M1 simulations shows the emergence of a neutrino trapped gas that locally decreases the temperature a few percent when compared to the other simulation series. This out-of-thermodynamics equilibrium effect does not alter the GW emission at the typical resolutions considered for mergers. Different microphysics treatments impact significantly mass, geometry and composition of the remnant’s disc and ejecta. M1 simulations show systematically larger proton fractions. The different ejecta compositions reflect into the nucleosynthesis yields, that are robust only if both neutrino emission and absorption are simulated. Synthetic kilonova light curves calculated by means of spherically-symmetric radiation-hydrodynamics evolutions up to 15 days post-merger are mostly sensitive to ejecta’s mass and composition; they can be reliably predicted only including the various ejecta components. We conclude that advanced microphysics in combination with resolutions higher than current standards appear essential for robust long-term evolutions and astrophysical predictions.

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F. Zappa, S. Bernuzzi, D. Radice, et. al.
Mon, 24 Oct 22
51/56

Comments: N/A

Post-Newtonian-accurate pulsar timing array signals induced by inspiralling eccentric binaries: accuracy and computational cost [CL]

http://arxiv.org/abs/2210.11454


Pulsar Timing Array (PTA) experiments are expected to be sensitive to gravitational waves (GWs) emitted by individual supermassive black hole binaries (SMBHBs) inspiralling along eccentric orbits. We compare the computational cost of different methods of computing the PTA signals induced by relativistic eccentric SMBHBs, namely approximate analytic expressions, Fourier series expansion, post-circular expansion, and numerical integration. We show that the fastest method for evaluating PTA signals is by using the approximate analytic expressions, providing up to a $\sim$50 times improvement in computational performance over the alternative methods. We investigate the accuracy of the approximate analytic expressions by employing a mismatch metric valid for PTA signals. We show that this method is accurate within the region of the binary parameter space that is of interest to PTA experiments. We introduce a spline-based method for further accelerating the PTA signal evaluations for narrow-band PTA datasets. These results are crucial for searching for eccentric SMBHBs in large PTA datasets. We have implemented these results in the GWecc package and can be readily accessed from the popular ENTERPRISE package to search for such signals in PTA datasets.

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A. Susobhanan
Fri, 21 Oct 22
6/76

Comments: Submitted to Classical and Quantum Gravity

Mapping the Weak-Field Limit of Scalar-Gauss-Bonnet Gravity [CL]

http://arxiv.org/abs/2210.10955


We derive the weak field limit of scalar-Gauss-Bonnet theory and place novel bounds on the parameter space using terrestrial and space-based experiments. In order to analyze the theory in the context of a wide range of experiments, we compute the deviations from Einstein gravity around source masses with planar, cylindrical, and spherical symmetry. We find a correction to the Newtonian potential around spherical and cylindrical sources that can be larger than PPN corrections sufficiently close to the source. We use this to improve on laboratory constraints on the scalar-Gauss-Bonnet coupling parameter $\Lambda$ by two orders of magnitude. Present laboratory and Solar System bounds reported here are superseded by tests deriving from black holes.

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B. Elder and J. Sakstein
Fri, 21 Oct 22
18/76

Comments: 18 pages

The Search for the Topology of the Universe Has Just Begun [CEA]

http://arxiv.org/abs/2210.11426


Anomalous large-angle cosmic microwave background anisotropies motivate further searches for cosmic topology. We demonstrate that for generic topologies of spatially flat spacetimes, off-diagonal correlations between microwave background harmonic coefficients over a wide range of scales encode significant topological information, even if the topology scale substantially exceeds the diameter of the observable Universe. Observational searches have so far considered only a small subset of testable topologies, and current limits on the topology scale are much weaker than generally understood.

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Y. Akrami, C. Copi, J. Eskilt, et. al.
Fri, 21 Oct 22
23/76

Comments: 7 pages, 3 figures

Identifying LISA verification binaries amongst the Galactic population of double white dwarfs [SSA]

http://arxiv.org/abs/2210.10812


Double white dwarfs (DWDs) will be the most numerous gravitational-wave (GW) sources for the Laser Interferometer Space Antenna (LISA). Most of the Galactic DWDs will be unresolved and will superpose to form a confusion noise foreground, the dominant LISA noise source around $\sim 0.5\mathrm{-}3\,\mathrm{mHz}$. A small fraction of these sources will stand out from the background and be individually detectable. Uniquely among GW sources, a handful of these binaries will be known in advance from electromagnetic observations and will be guaranteed sources of detectable GWs in the LISA band; these are known as verification binaries (VBs). High-cadence photometric surveys are continuously discovering new VB systems, and their number will continue to grow ahead of the launch of LISA. We analyse, in a fully Bayesian framework, all the currently known VBs with the latest design requirements for the LISA mission. We explore what can be expected from GW observations, both alone and in combination with electromagnetic observations, and estimate the VB’s time to detection in the early months of LISA operations. We also show how VBs can be analysed in the (realistic) case where their GW signals compete with many other unknown binary signals (both resolved and unresolved) from the Galactic population of DWDs.

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E. Finch, G. Bartolucci, D. Chucherko, et. al.
Fri, 21 Oct 22
24/76

Comments: 13 pages, 8 figures, plus appendices

Gravitational waves as waveguides [CL]

http://arxiv.org/abs/2210.09544


We show that gravitational waves can act as waveguides for electromagnetic radiation, that is if the latter is initially aligned with the gravitational waves, then the alignment will survive during the propagation. The analysis is performed using the Hamiltonian formalism and the Jacobi equation for null geodesics and conditions for certain cases of polarization of the waves are obtained. The effect of waveguiding by the gravitational waves can influence the interpretation of associated gravitational and electromagnetic wave events, since the latter cannot necessarily obey the inverse square decay law for intensity.

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A. A.A.Kocharyan, M. M.Samsonyan and V. V.G.Gurzadyan
Fri, 21 Oct 22
27/76

Comments: 8 pages, 2 figs; Eur Phys J Plus (in press)

Light speed variation from GRB 221009A [HEAP]

http://arxiv.org/abs/2210.11376


It is postulated in Einstein’s relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed, and a series of previous researches on high-energy photon events from gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) suggest a light speed variation $v(E)=c\left(1-E / E_{\mathrm{LV}}\right)$ with $E_{\mathrm{LV}}=3.6 \times 10^{17} ~\mathrm{GeV}$. From the newly detected gamma-ray burst GRB 221009A, we find that a $99.3~$GeV photon detected by Fermi-LAT is coincident with the sharp spike in the light curves detected by Fermi-GBM and HEBS under the above scenario of light speed variation, suggesting that this high energy photon was emitted at the same time with a sharp spike of low energy photon emission at the GRB source. Thus this highest energy photon event detected by Fermi-LAT during the prompt emission of gamma ray bursts supports the linear form modification of light speed in cosmological space.

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J. Zhu and B. Ma
Fri, 21 Oct 22
37/76

Comments: 4 latex pages, 2 figures

Generalized $R^p$-attractor Cosmology in the Jordan and Einstein Frames: New Type of Attractors and Revisiting Standard Jordan Frame $R^p$ Inflation [CL]

http://arxiv.org/abs/2210.11351


In this work we shall study a new class of attractor models which we shall call generalized $R^p$-attractor models. This class of models is based on a generalization of the Einstein frame potential of $R^p$ $f(R)$ gravity models in the Jordan frame. We present the attractor properties of the corresponding non-minimally coupled Jordan frame theory, and we calculate the observational indices of inflation in the Einstein frame. As we show, there is a large class of non-minimally coupled scalar theories, with an arbitrary non-minimal coupling which satisfies certain conditions, that yield the same Einstein frame potential, this is why these models are characterized attractors. As we demonstrate, the generalized $R^p$-attractor models are viable and well fitted within the Planck constraints. This includes the subclass of the generalized $R^p$-attractor models, namely the Einstein frame potential of $R^p$ inflation in the Jordan frame, a feature also known in the literature. We also highlight an important issue related to the $R^p$ inflation in the Jordan frame, which is known to be non-viable. By conformal invariance, the $R^p$ inflation model should also be viable in the Jordan frame, which is not. We pinpoint the source of the problem using two different approaches in the $f(R)$ gravity Jordan frame, and as we demonstrate, the problem arises in the literature due to some standard simplifications made for the sake of analyticity. We demonstrate the correct way to analyze $R^p$ inflation in the Jordan frame, using solely the slow-roll conditions.

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S. Odintsov and V. Oikonomou
Fri, 21 Oct 22
75/76

Comments: IJMPD Accepted

Why is zero spatial curvature special? [CEA]

http://arxiv.org/abs/2210.10102


Evidence for almost spatial flatness of the Universe has been provided from several observational probes, including the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO) from galaxy clustering data. However, other than inflation, and in this case only in the limit of infinite time, there is no strong a priori motivation for a spatially flat Universe. Using the renormalization group (RG) technique in curved spacetime, we present in this work a theoretical motivation for spatial flatness. Starting from a general spacetime, the first step of the RG, coarse-graining, gives a Friedmann-Lema\^itre-Robertson-Walker (FLRW) metric with a set of parameters. Then, we study the rescaling properties of the curvature parameter, and find that zero spatial curvature of the FLRW metric is singled out as the unique scale-free, non-singular background for cosmological perturbations.

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R. Jimenez, A. Khalife, D. Litim, et. al.
Thu, 20 Oct 22
5/74

Comments: N/A

Distinguishing a Slowly Accelerating Black Hole by Differential Time Delays of Images [CL]

http://arxiv.org/abs/2210.10762


Accelerating supermassive black holes, connected to cosmic strings, could contribute to structure formation and get captured by galaxies if their velocities are small. This would mean that the acceleration of these black holes is small too. Such a slow acceleration has no significant effect on the shadow of such supermassive black holes. We also show that, for slowly accelerating black holes, the angular position of images in the gravitational lensing effects do not change significantly. We propose a method to observe the acceleration of these black holes through the gravitational lensing. The method is based on the observation that differential time delays associated with the images are substantially different with respect to the case of non-accelerating black holes.

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A. Ashoorioon, M. Poshteh and R. Mann
Thu, 20 Oct 22
6/74

Comments: 5 pages, 3 figures, matched the published version in PRL. arXiv admin note: substantial text overlap with arXiv:2110.13132

Improving the spin-down limits for the continuous gravitational waves emitted from pulsars as triaxial rotators [HEAP]

http://arxiv.org/abs/2210.10355


The spin-down limit of the continuous gravitational wave strain (assuming pulsars as triaxial rotators) depends upon the value of the intrinsic spin frequency derivative of the pulsar, among other parameters. In order to get more accurate intrinsic spin frequency derivative values, dynamical effects contributing to the measured spin frequency derivative values must be estimated via more realistic approaches. In this work, we calculate improved values of the spin-down limit of the gravitational wave strain (assuming pulsars as triaxial rotators) for a set of 237 pulsars for which a targeted search for continuous gravitational waves was carried out by the LVK Collaboration, recently. We use `GalDynPsr’, a python-based public package, to calculate more realistic values of intrinsic spin frequency derivatives, and consequently, we get, more realistic values of the spin-down limit. For 136 pulsars, we obtain a higher value of the spin-down limit as compared to recently estimated values by the LVK Collaboration.

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D. Pathak and D. Chatterjee
Thu, 20 Oct 22
14/74

Comments: 7 pages

Reconstructing inflation and reheating in $f(φ)T$ gravity [CL]

http://arxiv.org/abs/2210.10080


The reconstruction of an inflationary universe in the context of one $f(\phi)T$ gravity, in which $T$ corresponds to the trace of energy momentum tensor is studied. To realize this reconstruction during the inflationary epoch, we consider as attractor the scalar spectral index $n_s$ in terms of of the number of $e$-folds $N$, in the framework of the slow-roll approximation. By assuming a specific function $f(\phi)$ together with the simplest attractor $n_s(N)$, we find different expressions for the reconstructed effective potential $V(\phi)$. Additionally, we analyze the era of reheating occurs after of the reconstruction obtained during the inflationary epoch. In this scenario we determine the duration and temperature during the reheating epoch, in terms of the equation of state parameter and the observational parameters. In this context, the different parameters associated to the reconstructed model are restricted during the scenarios of inflation and reheating by considering the recent astronomical observations.

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R. Herrera and C. Rios
Thu, 20 Oct 22
26/74

Comments: 16 pages and 6 figures

Rapster: a fast code for dynamical formation of black-hole binaries in dense star clusters [HEAP]

http://arxiv.org/abs/2210.10055


Gravitational-wave observations have just started probing the properties of black-hole binary merger populations. The observation of binaries with very massive black holes and small mass ratios motivates the study of dense star clusters as astrophysical environments which can produce such events dynamically. In this paper we present Rapster (for “Rapid cluster evolution”), a new code designed to rapidly model binary black hole population synthesis and the evolution of star clusters based on simple, yet realistic prescriptions. The code can be used to generate large populations of dynamically formed binary black holes. It makes use of existing packages such as SEVN to model the initial black hole mass spectrum, and PRECESSION to model the mass, spin and gravitational recoil of merger remnants. We demonstrate that the event rates and population properties predicted by Rapster are in good agreement with other state-of-the-art codes.

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K. Kritos, V. Strokov, V. Baibhav, et. al.
Thu, 20 Oct 22
31/74

Comments: 30 pages, 13 figures, 5 tables, open source code available at this https URL

Inflation and Electroweak Symmetry Breaking [CL]

http://arxiv.org/abs/2210.10735


We present a model of Cosmological Electroweak Symmetry Breaking (CEWSB), where a Higgs-like field and a cosmological background of weak boson gauge fields interact with gravity to realize the epoch of cosmic inflation, which is then followed by a Higgs resonance preheating. As a result, the scale of electroweak symmetry breaking is linked with the end of inflation. The theory is equipped with a shift symmetry that can protect the Higgs mass, and it has close semblance to natural inflation and its variants. As the Higgs field’s amplitude decays at the end of inflation, its mass emerges. The model has a built in Higgs self-resonance preheating mechanism which leads to the possible emergence of the cosmic microwave background (CMB) due to resonant Higgs, quark and lepton production after inflation. We provide a pathway to implement a similar mechanism with the realistic Higgs-doublet of the standard electroweak theory and discuss phenomenological considerations.

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S. Alexander
Thu, 20 Oct 22
36/74

Comments: 7 pages

Extensions of two-field mimetic gravity [CL]

http://arxiv.org/abs/2210.10499


Two-field mimetic gravity was recently realized by looking at the singular limit of the conformal transformation between the auxiliary metric and the physical metric with two scalar fields involved. In this paper, we reanalyze the singular conformal limit and find a more general solution for the conformal factor A, which greatly broadens the form of two-field mimetic constraint and thus extends the two-field mimetic gravity. We find the general setup still mimics the roles of dark matter at the cosmological background level. Moreover, we extend the action by introducing extra possible term for phenomenological interests. Surprisingly, some special cases are found to be equivalent to general relativity, k-essence theory and Galileon theory. Finally, we further extend the theory by allowing the expression of mimetic constraint to be arbitrary without imposed condition, and show that the dark matter-like behavior is unaffected even in this extension.

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Y. Zheng and H. Rao
Thu, 20 Oct 22
64/74

Comments: 17 pages, comments are welcome

Radial Oscillations and Dynamical Instability Analysis for Linear GUP-modified White Dwarfs [CL]

http://arxiv.org/abs/2210.09876


A modification to the Heisenberg uncertainty principle is called the generalized uncertainty principle (GUP), which emerged due to the introduction of a minimum measurable length, common among phenomenological approaches to quantum gravity. An approach to GUP called linear GUP (LGUP) has recently been developed that satisfies both the minimum measurable length and the maximum measurable momentum, resulting to a phase space volume proportional to the first-order momentum $(1 – \alpha p)^{-4} d^3x d^3p$, where $\alpha$ is the still-unestablished GUP parameter. In this study, we explore the mass-radius relations of LGUP-modified white dwarfs, and provide them with radial perturbations to investigate the dynamical instability arising from the oscillations. We find from the mass-radius relations that LGUP results to a white dwarf with a lower maximum mass, and this effect gets more apparent with larger the values of $\alpha$. We also observe that the mass of the white dwarf corresponding to the vanishing of the square of the fundamental frequency $\omega_0$ is the maximum mass the white dwarf can have in the mass-radius relations. The dynamical instability analysis also shows that instability sets in for all values of the GUP parameters $\alpha$, and at lower central densities $\rho_c$ (corresponding to lower maximum masses) for increasing $\alpha$, which verifies the results obtained from the mass-radius relations plots. Finally, we note that the mass limit is preserved for LGUP-modified white dwarfs, indicating that LGUP supports gravitational collapse of the compact object.

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J. Bernaldez, A. Abac and R. Otadoy
Wed, 19 Oct 22
5/87

Comments: N/A

Does the gamma-ray binary LS I +61 303 harbour a magnetar? [HEAP]

http://arxiv.org/abs/2210.09471


LS I +61{\deg}303 is a high mass X-ray binary that is also catalogued as a gamma-ray binary as a result of frequent outbursts at TeV photon energies. The system has released two soft-gamma flares in the past, suggesting a magnetar interpretation for the compact primary. This inference has recently gained significant traction following the discovery of transient radio pulses, detected in some orbital phases from the system, as the measured rotation and tentative spindown rates imply a polar magnetic field strength of $B_p \gtrsim 10^{14}\,\mbox{G}$ if the star is decelerating via magnetic dipole braking. In this paper, we scrutinise magnetic field estimates for the primary in LS I +61{\deg}303 by analysing the compatibility of available data with the system’s accretion dynamics, spin evolution, age limits, gamma-ray emissions, and radio pulsar activation. We find that the neutron star’s age and spin evolution are theoretically difficult to reconcile unless a strong propeller torque is in operation. This torque could be responsible for the bulk of even the maximum allowed spindown, potentially weakening the inferred magnetic field by more than an order of magnitude.

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A. Suvorov and K. Glampedakis
Wed, 19 Oct 22
17/87

Comments: 12 pages, 5 figures. Accepted for publication in ApJ

Revealing the effects of curvature on the cosmological models [CEA]

http://arxiv.org/abs/2210.09865


In this paper we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic microwave background temperature and polarization data, Baryon Acoustic Oscillations and Pantheon type Ia Supernovae data. Our main result is that a non-flat Universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed Universe in most of the DE cosmologies explored in this work. On the other hand, forcing the Universe to be flat can significantly bias the constraints on the equation of state of the DE component and its dynamical nature.

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W. Yang, W. Giarè, S. Pan, et. al.
Wed, 19 Oct 22
25/87

Comments: 40 pages, 17 tables and 22 captioned figures

Gravitational-wave imprints of compact and galactic-scale environments in extreme-mass-ratio binaries [CL]

http://arxiv.org/abs/2210.09357


Circumambient and galactic-scale environments are intermittently present around black holes, especially those residing in active galactic nuclei. As supermassive black holes impart energy on their host galaxy, so the galactic environment affects the geodesic dynamics of solar-mass objects around supermassive black holes and subsequently the gravitational waves emitted from such non-vacuum extreme-mass-ratio binaries. Only recently an exact general-relativistic solution has been found that describes a Schwarzschild black hole immersed in a dark matter halo profile of the Hernquist type. We perform an extensive geodesic analysis of test particles delving in such non-vacuum spacetimes and compare our results with those obtained in vacuum Schwarzschild spacetime, as well as their dominant gravitational-wave emission. Our findings indicate that the radial and polar oscillation frequency ratios, which indicate resonances, descend deeper into the extreme gravity regime as the compactness of the halo increases. This translates to a gravitational redshift of non-vacuum geodesics and their resulting waveforms with respect to the vacuum ones; a phenomenon which has also been observed for ringdown signals in these setups. For compact environments, we find that the apsidal precession of orbits is strongly affected due to the gravitational pull of dark matter; the orbit’s axis can rotate in the opposite direction as that of the orbital motion, leading to a retrograde precession drift that depends on the halo’s mass, as opposed to the typical prograde precession transpiring in vacuum and galactic-scale environments. Gravitational waves in retrograde-to-prograde orbital alterations demonstrate transient frequency phenomena around a critical non-precessing turning point, thus they may serve as a `smoking gun’ for the presence of dense dark matter environments around supermassive black holes.

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K. Destounis, A. Kulathingal, K. Kokkotas, et. al.
Wed, 19 Oct 22
28/87

Comments: 14 pages, 7 figures

New Constraints on Dark Matter and Cosmic Neutrino Profiles through Gravity [CL]

http://arxiv.org/abs/2210.03749


We derive purely gravitational constraints on dark matter and cosmic neutrino profiles in the solar system using asteroid (101955) Bennu. We focus on Bennu because of its extensive tracking data and high-fidelity trajectory modeling resulting from the OSIRIS-REx mission. We find that the local density of dark matter is bound by $\rho_{\rm DM}\lesssim 3.3\times 10^{-15}\;\rm kg/m^3 \simeq 6\times10^6\,\bar{\rho}{\rm DM}$, in the vicinity of $\sim 1.1$ au (where $\bar{\rho}{\rm DM}\simeq 0.3\;\rm GeV/cm^3$). We show that high-precision tracking data of solar system objects can constrain cosmic neutrino overdensities relative to the Standard Model prediction $\bar{n}{\nu}$, at the level of $\eta\equiv n\nu/\bar{n}{\nu}\lesssim 1.7 \times 10^{11}(0.1 \;{\rm eV}/m\nu)$ (Saturn), comparable to the existing bounds from KATRIN and other previous laboratory experiments (with $m_\nu$ the neutrino mass). These local bounds have interesting implications for existing and future direct-detection experiments. Our constraints apply to all dark matter candidates but are particularly meaningful for scenarios including solar halos, stellar basins, and axion miniclusters, which predict or allow overdensities in the solar system. Furthermore, introducing a DM-SM long-range fifth force with a strength $\tilde{\alpha}D$ times stronger than gravity, Bennu can set a constraint on $\rho{\rm DM}\lesssim \bar{\rho}_{\rm DM}\left(6 \times 10^6/\tilde{\alpha}_D\right)$. These constraints can be improved in the future as the accuracy of tracking data improves, observational arcs increase, and more missions visit asteroids.

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Y. Tsai, J. Eby, J. Arakawa, et. al.
Wed, 19 Oct 22
33/87

Comments: 2 figures, 2 tables, 9 pages plus references

Search for continuous gravitational waves from HESS~J1427-608 with a hidden Markov model [HEAP]

http://arxiv.org/abs/2210.09592


We present a search for continuous gravitational wave signals from an unidentified pulsar potentially powering HESS J1427-608, a spatially-unresolved TeV point source detected by the High Energy Stereoscopic System (H.E.S.S). The search uses a semi-coherent algorithm, which combines the maximum likelihood $\mathcal{F}-$statistic with a hidden Markov Model to efficiently detect and track quasi-monochromatic signals that wander randomly in frequency. It uses data from the second observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory. Multi-wavelength observations of the H.E.S.S. source are combined with the proprieties of the population of TeV-bright pulsar wind nebulae to constrain the search parameters. We find no evidence of gravitational-wave emission from this target. We set upper limits on the characteristic wave strain $h_0^{95\%}$ (for circularly-polarised signals) at $95\%$ confidence level in sample sub-bands and interpolate it to estimate the sensitivity in the full band. We find $h_0^{95\%} = 1.3\times 10^{-25}$ near 185~Hz. The implied constraints on the ellipticity and r-mode amplitude reach $\epsilon\leq 10^{-5}$ and $\alpha \leq 10^{-3}$ at 200~Hz, respectively.

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D. Beniwal, P. Clearwater, L. Dunn, et. al.
Wed, 19 Oct 22
38/87

Comments: 16 pages, 7 figures

Upper limits on the Polarized Isotropic Stochastic Gravitational-Wave Background from Advanced LIGO-Virgo's First Three Observing Runs [CEA]

http://arxiv.org/abs/2210.09952


Parity violation is expected to generate an asymmetry between the amplitude of left and right-handed gravitational-wave modes which leads to a circularly polarized stochastic gravitational-wave background (SGWB). Due to the three independent baselines in the LIGO-Virgo network, we focus on the amplitude difference in strain power characterized by Stokes’ parameters and do maximum-likelihood estimation to constrain the polarization degree of SGWB. Our results indicate that there is no evidence for the circularly polarized SGWB in the data. Furthermore, by modeling the SGWB as a power-law spectrum, we place upper limit on the normalized energy density $\Omega_\text{gw}(25\,\text{Hz})<5.3\times10^{-9}$ at $95\%$ confidence level after marginalizing over the polarization degree and spectral index.

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Y. Jiang and Q. Huang
Wed, 19 Oct 22
42/87

Comments: 6 pages, 4 figures and 2 tables

Breaking Bad Degeneracies with Love: Improving gravitational-wave measurements through universal relations [CL]

http://arxiv.org/abs/2210.09386


The distance-inclination degeneracy limits gravitational-wave parameter estimation of compact binary mergers. Although the degeneracy can be partially broken by including higher-order modes or precession, these effects are suppressed in binary neutron stars. In this work we implement a new parameterization of the tidal effects in the binary neutron star waveform, exploiting the binary Love relations, that breaks the distance-inclination degeneracy. The binary Love relations prescribe the tidal deformability of a neutron star as a function of its source-frame mass in an equation-of-state insensitive way, and thus allows direct measurement of the redshift of the source. If the cosmological parameters are assumed to be known, the redshift can be converted to a luminosity distance, and the distance-inclination degeneracy can thus be broken. We implement this new approach, studying a range of binary neutron-star observing scenarios using Bayesian parameter estimation on synthetic data. In the era of the third generation detectors, for observations with signal-to-noise ratios ranging from 6 to 167, we forecast up to a $\sim70\%$ decrease in the $90\%$ credible interval of the distance and inclination, and up to a $\sim50\%$ decrease in that of the source-frame component masses. For edge-on systems, our approach can result in moderate ($\sim50\%$) improvement in the measurements of distance and inclination for binaries with signal-to-noise ratio as low as 10. This prescription can be used to better infer the source-frame masses, and hence refine population properties of neutron stars, such as their maximum mass, impacting nuclear astrophysics. When combined with the search for electromagnetic counterpart observations, the work presented here can be used to put improved bounds on the opening angle of jets from binary neutron star mergers.

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Y. Xie, D. Chatterjee, G. Holder, et. al.
Wed, 19 Oct 22
51/87

Comments: 18 pages, 12 figures, submitted to PRD

Scaling solutions of wiggly cosmic strings: II. Time-varying coarse-graining scale solutions [CEA]

http://arxiv.org/abs/2210.09801


We continue our exploration of the wiggly generalisation of the Velocity-Dependent One Scale Model for cosmic strings, through the study of its allowed asymptotic scaling solutions. We extend the work of a previous paper [Almeida $\&$ Martins, Phys. Rev. D 104 (2021) 043524] by considering the more comprehensive case of a time-varying coarse-graining scale for the string wiggles. The modeling of the evolution of the network therefore relies on three main mechanisms: Hubble expansion, energy transfer mechanisms (e.g., the production of loops and wiggles) and the choice of the scale at which wiggles are coarse-grained. We analyse the role of each of them on the overall behaviour of the network, and thus in the allowed scaling solutions. In Minkowski space, we find that linear scaling, previously observed in numerical simulations without expansion, is not possible with a changing averaging scale. For expanding universes, we find that the three broad classes of scaling solutions — with the wiggliness disappearing, reaching scaling, or growing — still exist but are differently impacted by the time evolution of the coarse-graining scale. Nambu-Goto type solutions (without wiggles) are unaffected, growing wiggliness solutions are trivially generalized, while for solutions where wiggliness reaches scaling the expansion rate for which the solution exists is decreased with respect to the one for a fixed coarse-graining scale. Finally, we also show that the inclusion of a time-varying coarse-graining scale allows, in principle, for additional scaling solutions which, although mathematically valid, are not physical. Overall, our mapping of the landscape of the allowed scaling solutions of the wiggly Velocity-Dependent One Scale Model paves the way for the detailed testing of the model, to be done by forthcoming high-resolution field theory and Nambu-Goto simulations.

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A. Almeida and C. Martins
Wed, 19 Oct 22
58/87

Comments: 15 pages, 6 figures, 1 table; Phys. Rev. D (in press). Second paper in a series, the first one is arXiv: 2107.11653. Some particular solutions were previously reported in a conference proceedings at arXiv:2210.08467

A new Parametrization for Bulk Viscosity Cosmology as Extension of the $Λ$CDM Model [CL]

http://arxiv.org/abs/2210.09429


Bulk viscosity in cold dark matter is an appealing feature that introduces distinctive phenomenological effects in the cosmological setting as compared to the $\Lambda$CDM model. Under this view, we propose a general parametrization of the bulk viscosity of the form $\xi\sim H^{1-2s} \rho_{m}^{s}$, that covers intriguingly some well-known cases in the Eckart’s theory. Some advantages of this novel parametrization are: first, it allows to write the resulting equations of cosmological evolution in the form of an autonomous system for any value of $s$, so a general treatment of the fixed points and stability can be done, and second, the bulk viscosity effect is consistently handled so that it naturally turns off when matter density vanishes. As a main result we find, based on detailed dynamical system analysis, one-parameter family of de-Sitter-like asymptotic solutions with non-vanishing bulk viscosity coefficient during different cosmological periods. Numerical computations are performed jointly along with analytical phase space analysis in order to assess more quantitatively the bulk viscosity effect on the cosmological background evolution. Finally, as a first contact with observation we derive constraints on the free parameters of some bulk viscosity models with specific $s$-exponents from Supernovae Ia and observations of the Hubble parameter, by performing a Bayesian statistical analysis thought the Markov Chain Monte Carlo method.

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L. Gómez, G. Palma, &. Rincón, et. al.
Wed, 19 Oct 22
67/87

Comments: 24 pages, 5 figures. Comments are welcome

Prospects for detecting transient quasi-monochromatic gravitational waves from glitching pulsars with current and future detectors [HEAP]

http://arxiv.org/abs/2210.09907


Pulsars are rotating neutron stars that emit periodic electromagnetic radiation. While pulsars generally slow down as they lose energy, some also experience glitches: spontaneous increases of their rotational frequency. According to several models, these glitches can also lead to the emission of long-duration transient gravitational waves (GWs). We present detection prospects for such signals by comparing indirect energy upper limits on GW strain for known glitches with the sensitivity of current and future ground-based GW detectors. We first consider generic constraints based on the glitch size and find that realistic matched-filter searches in the fourth LIGO-Virgo-KAGRA observing run (O4) could make a detection, or set constraints below these indirect upper limits, for equivalents of 36 out of 726 previously observed glitches, and 74 in the O5 run. With the third-generation Einstein Telescope or Cosmic Explorer, 35-40% of glitches would be accessible. When specialising to a scenario where transient mountains produce the post-glitch GW emission, following Yim & Jones (2020), the indirect upper limits are stricter. Out of the smaller set of 119 glitches with measured healing parameter, as needed for predictions under that model, only 6 glitches would have been within reach for O4 and 14 for O5, with a similar percentage as before with third generation detectors. We also discuss how this model matches the observed glitch population.

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J. Moragues, L. Modafferi, R. Tenorio, et. al.
Wed, 19 Oct 22
72/87

Comments: 16 pages, 9 figures, comments welcome

Equation of State and Mass-Radius Relations of Quadratic Generalized Uncertainty Principle-modified White Dwarfs with Arbitrary Temperatures [CL]

http://arxiv.org/abs/2210.09886


We study the mass-radius relations of finite temperature white dwarfs modified by the quadratic generalized uncertainty principle (QGUP), a prediction that arises from quantum gravity phenomenology. This QGUP approach extends the Heisenberg uncertainty principle by a quadratic term in momenta, which then modifies the phase space volume in the Chandrasekhar equation of state (EoS). This EoS was first calculated by treating the GUP parameter $\beta$ as perturbative. This perturbative EoS exhibits the expected thermal deviation for low pressures, while showing conflicting behaviors in the high pressure regime dependent on the sign of the $j$th order of approximation, $(\mathcal{O}(\beta^j))$. To explore the effects of QGUP further, we proceed with a full numerical simulation, and showed that in general, finite temperatures cause the EoS at low pressures to soften, while QGUP stiffens the EOS at high pressures. This modified EoS was then applied to the Tolman-Oppenheimer-Volkoff equations and its classical approximation to obtain the modified mass-radius relations for general relativistic and Newtonian white dwarfs. The relations for both cases were found to exhibit the expected thermal deviations at small masses, where low-mass white dwarfs are shifted to the high-mass regime at large radii, while high-mass white dwarfs acquire larger masses, beyond the Chandrasekhar limit. Additionally, we find that for sufficiently large values of the GUP parameter and temperature, we obtain mass-radius relations that are completely removed from the ideal case, as high-mass deviations due to GUP and low-mass deviations due to temperature are no longer mutually exclusive.

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J. Tuñacao, A. Abac and R. Otadoy
Wed, 19 Oct 22
78/87

Comments: N/A

Impact of updated Multipole Love and f-Love Universal Relations in context of Binary Neutron Stars [HEAP]

http://arxiv.org/abs/2210.09425


Neutron star (NS) equation of state (EoS) insensitive relations or universal relations (UR) involving neutron star bulk properties play a crucial role in gravitational-wave astronomy. Considering a wide range of equations of state originating from (i) phenomenological relativistic mean field models, (ii) realistic EoS models based on different physical motivations, and (iii) polytropic EoSs described by spectral decomposition method, we update the EoS-insensitive relations involving NS tidal deformability (Multipole Love relation) and the UR between f-mode frequency and tidal deformability (f-Love relation). We analyze the binary neutron star (BNS) event GW170817 using the frequency domain TaylorF2 waveform model with updated universal relations and find that the additional contribution of the octupolar electric tidal parameter and quadrupolar magnetic tidal parameter or the change of multipole Love relation has no significant impact on the inferred NS properties. However, adding the f-mode dynamical phase lowers the 90% upper bound on $\tilde{\Lambda}$ by 16-20% as well as lowers the upper bound of NSs radii by $\sim$500m. The combined URs (multipole Love and f-Love) developed in this work predict a higher median (also a higher 90% upper bound) for $\tilde{\Lambda}$ by 6% and also predict higher radii for the binary components of GW170817 by 200-300m compared to the URs used previously in the literature. We further perform injection and recovery studies on simulated events with different EoSs in $\rm A+$ detector configuration as well as with third generation (3G) Einstein telescope. In agreement with the literature, we find that neglecting f-mode dynamical tides can significantly bias the inferred NS properties, especially for low mass NSs. However, we also find that the impact of the URs is within statistical errors.

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B. Pradhan, A. Vijaykumar and D. Chatterjee
Wed, 19 Oct 22
80/87

Comments: 21 pages,10 figures

Constraints on Late Time Violations of the Equivalence Principle in the Dark Sector [CL]

http://arxiv.org/abs/2210.09732


If dark energy is dynamical due to the evolution of a scalar field, then in general it is expected that the scalar is coupled to matter. While couplings to the standard model particles are highly constrained by local experiments, bounds on couplings to dark matter (DM) are only obtained from cosmological observations and they are consequently weaker. It has recently be pointed out that the coupling itself can become non-zero only at the time of dark energy domination, due to the evolution of dark energy itself, leading to a violation of the equivalence principle (EP) in the dark sector at late times. In this paper we study a specific model and show that such late-time violations of the EP in the DM sector are not strongly constrained by the evolution of the cosmological background and by observables in the linear regime (e.g. from the cosmic microwave background radiation). A study of perturbations in non-linear regime is necessary to constrain late–time violations of the equivalence principle much more strongly.

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C. Thomas and C. Bruck
Wed, 19 Oct 22
81/87

Comments: 9 pages, 3 figures, 2 tables

Stellar structure model in the post-Newtonian approximation [CL]

http://arxiv.org/abs/2210.08105


In this work the influence of the post-Newtonian corrections to the equations of stellar structure is analysed. The post-Newtonian Lane-Emden equation follows from the corresponding momentum density balance equation. From a polytropic equation of state the solutions of the Lane-Endem equations in the Newtonian and post-Newtonian theories are determined and the physical quantities for the \textit{Sun}, for the white dwarf \textit{Sirius B} and for neutron stars with masses $M\simeq1.4M_\odot, 1.8M_\odot$ and $2.0M_\odot$ are calculated. It is shown that the post-Newtonian corrections to the fields of mass density, pressure and temperature are negligible for the \textit{Sun} and \textit{Sirius B}, but for stars with strong fields the differences become important. For the neutron stars analysed here the central pressure and the central temperature which follow from the post-Newtonian Lane-Emden equation are about fifty to sixty percent greater than those of the Newtonian theory and the central mass density is about three to four percent smaller.

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G. Kremer
Tue, 18 Oct 22
25/99

Comments: 8 pages, 3 figures

Frame-Dragging in Extrasolar Circumbinary Planetary Systems [CL]

http://arxiv.org/abs/2210.09154


Extrasolar circumbinary planets are so called because they orbit two stars instead of just one; to date, an increasing number of such planets have been discovered with a variety of techniques. If the orbital frequency of the hosting stellar pair is much higher than the planetary one, the tight stellar binary can be considered as a matter ring current generating its own post-Newtonian stationary gravitomagnetic field through its orbital angular momentum. It affects the orbital motion of a relatively distant planet with Lense-Thirring-type precessional effects which, under certain circumstances, may amount to a significant fraction of the static, gravitoelectric ones, analogous to the well known Einstein perihelion precession of Mercury, depending only on the masses of the system’s bodies. Instead, when the gravitomagnetic field is due solely to the spin of each of the central star(s), the Lense-Thirring shifts are several orders of magnitude smaller than the gravitoelectric ones. In view of the growing interest in the scientific community about the detection of general relativistic effects in exoplanets, the perspectives of finding new scenarios for testing such a further manifestation of general relativity might be deemed worth of further investigations.

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L. Iorio
Tue, 18 Oct 22
30/99

Comments: LaTex2e, 15 pages, no tables, 2 figures. Accepted for publication in Universe

Unraveling information about supranuclear-dense matter from the complete binary neutron star coalescence process using future gravitational-wave detector networks [CL]

http://arxiv.org/abs/2210.09259


Gravitational waves provide us with an extraordinary tool to study the matter inside neutron stars. In particular, the postmerger signal probes an extreme temperature and density regime and will help reveal information about the equation of state of supranuclear-dense matter. Although current detectors are most sensitive to the signal emitted by binary neutron stars before the merger, the upgrades of existing detectors and the construction of the next generation of detectors will make postmerger detections feasible. For this purpose, we present a new analytical, frequency-domain model for the inspiral-merger-postmerger signal emitted by binary neutron stars systems. The inspiral and merger part of the signals are modeled with IMRPhenomD$_$NRTidalv2, and we describe the main emission peak of postmerger with a three-parameter Lorentzian, using two different approaches: one in which the Lorentzian parameters are kept free, and one in which we model them via quasi-universal relations. We test the performance of our new complete waveform model in parameter estimation analyses, both with simulated signals and numerical relativity waveforms. We investigate the performance of different detector networks to determine the improvement that future detectors will bring to our analysis. We consider Advanced LIGO+ and Advanced Virgo+, KAGRA, and LIGO-India. We also study the possible impact of a detector with high sensitivity in the kilohertz band like NEMO, and finally we compare these results to the ones we obtain with third-generation detectors, the Einstein Telescope and the Cosmic Explorer.

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A. Puecher, T. Dietrich, K. Tsang, et. al.
Tue, 18 Oct 22
37/99

Comments: N/A

On thermal false vacuum decay around black holes [CL]

http://arxiv.org/abs/2210.08028


In flat space and at finite temperature, there are two regimes of false vacuum decay in quantum field theory. At low temperature, the decay proceeds through thermally-assisted tunneling described by periodic Euclidean solutions — bounces — with non-trivial time dependence. On the other hand, at high temperature the bounces are time-independent and describe thermal jumps of the field over the potential barrier. We argue that only solutions of the second type are relevant for false vacuum decay catalyzed by a black hole in equilibrium with thermal bath. The argument applies to a wide class of spherical black holes, including $d$-dimensional AdS/dS-Schwarzschild black holes and Reissner-Nordstr\”om black holes sufficiently far from criticality. It does not rely on the thin-wall approximation and applies to multi-field scalar theories.

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V. Briaud, A. Shkerin and S. Sibiryakov
Tue, 18 Oct 22
57/99

Comments: 7 pages, 2 figures

Scaling Solutions of Wiggly Cosmic Strings [CEA]

http://arxiv.org/abs/2210.08467


Cosmic string networks form during cosmological phase transitions as a consequence of the Kibble mechanism. The evolution of the simplest networks is accurately described by the canonical Velocity Dependent One-Scale (VOS) model. However, numerical simulations have demonstrated the existence of significant quantities of short-wavelength propagation modes on the strings, known as wiggles, which motivated the recent development of a wiggly string extension of the VOS. Here we summarize recent progress in the physical interpretation of this model through a systematic study of the allowed asymptotic scaling solutions of the model. The modeling mainly relies on three mechanisms: the universe’s expansion rate, energy transfer mechanisms (e.g., the production of loops and wiggles), and the choice of the scale in which wiggles are coarse-grained. We consider the various limits in which each mechanism dominates and compare the scaling solutions for each case, in order to gain insight into the role of each mechanism in the overall behavior of the network. Our results show that there are three scaling regimes for the wiggliness, consisting of the well-known Nambu-Goto solution, and non-trivial regimes where the amount of wiggliness can grow as the network evolves or, for specific expansion rates, become a constant. We also demonstrate that full scaling of the network is more likely in the matter era than in the radiation epoch, in agreement with numerical simulations.

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A. Almeida and C. Martins
Tue, 18 Oct 22
69/99

Comments: Summary of a talk given at the From Cosmic Strings to Superstrings parallel session of the Sixteenth Marcel Grossmann Meeting, partially summarizing work previously reported in arXiv:2107.11653, and some extensions thereof. To appear in the proceedings

Imprint of f(R) gravity in the cosmic magnification [CEA]

http://arxiv.org/abs/2210.09303


f(R) gravity is one of the simplest viable modifications to General Relativity: it passes local astrophysical tests, predicts both the early-time cosmic inflation and the late-time cosmic acceleration, and also describes dark matter. In this paper, we probe cosmic magnification on large scales in f (R) gravity, using the well-known Hu-Sawicki model as an example. Our results indicate that at redshifts z < 3, values of the model exponent n > 1 lead to inconsistent behaviour in the evolution of scalar perturbations. Moreover, when relativistic effects are taken into account in the large scale analysis, our results show that as z increases, large-scale changes in the cosmic magnification angular power spectrum owing to integral values of n tend to share a similar pattern, while those of decimal values tend to share another. This feature could be searched for in the experimental data, as a potential “smoking gun” for the given class of gravity models. Furthermore, we found that at z = 1 and lower, relativistic effects lead to a suppression of the cosmic magnification on large scales in f(R) gravity, relative to the concordance model; whereas, at z > 1, relativistic effects lead to a relative boost of the cosmic magnification. In general, relativistic effects enhance the potential of the cosmic magnification as a cosmological probe.

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D. Duniya, A. Abebe, A. Cruz-Dombriz, et. al.
Tue, 18 Oct 22
79/99

Comments: 14 pages, 4 figures

Machine-Learning Love: classifying the equation of state of neutron stars with Transformers [IMA]

http://arxiv.org/abs/2210.08382


The use of the Audio Spectrogram Transformer (AST) model for gravitational-wave data analysis is investigated. The AST machine-learning model is a convolution-free classifier that captures long-range global dependencies through a purely attention-based mechanism. In this paper a model is applied to a simulated dataset of inspiral gravitational wave signals from binary neutron star coalescences, built from five distinct, cold equations of state (EOS) of nuclear matter. From the analysis of the mass dependence of the tidal deformability parameter for each EOS class it is shown that the AST model achieves a promising performance in correctly classifying the EOS purely from the gravitational wave signals, especially when the component masses of the binary system are in the range $[1,1.5]M_{\odot}$. Furthermore, the generalization ability of the model is investigated by using gravitational-wave signals from a new EOS not used during the training of the model, achieving fairly satisfactory results. Overall, the results, obtained using the simplified setup of noise-free waveforms, show that the AST model, once trained, might allow for the instantaneous inference of the cold nuclear matter EOS directly from the inspiral gravitational-wave signals produced in binary neutron star coalescences.

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G. Gonçalves, M. Ferreira, J. Aveiro, et. al.
Tue, 18 Oct 22
86/99

Comments: 11 pages, 11 figures

Black hole merger simulations in wave dark matter environments [CL]

http://arxiv.org/abs/2210.09254


The interaction of binary black hole mergers with their environments can be studied using numerical relativity simulations. These start only a short finite time before merger, at which point appropriate initial conditions must be imposed. A key task is therefore to identify the configuration that is appropriate for the binary and its environment at this stage of the evolution. In this work we study the behaviour of wave dark matter around equal mass black hole binaries, finding that there is a preferred, quasi-stationary profile that persists and grows over multiple orbits, in contrast to heavier mass dark matter where any overdensity tends to be dispersed by the binary motion. Whilst different initial configurations converge to the preferred quasi-stationary one after several orbits, unwanted transient oscillations are generated in the process, which may impact on the signal in short simulation runs. We also point out that naively superimposing the matter onto a circular binary results in artificially eccentric orbits due to the matter backreaction, which is an effect of the initial conditions and not a signature of dark matter. We discuss the further work required so that comparison of waveforms obtained with environments to vacuum cases can be done in a meaningful way.

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J. Bamber, J. Aurrekoetxea, K. Clough, et. al.
Tue, 18 Oct 22
96/99

Comments: 9 pages, 5 figures, 1 appendix, 2 movies: this https URL Comments welcome!

Periapsis shift of a quasi-circular orbit in a general static spherically symmetric spacetime [CL]

http://arxiv.org/abs/2210.07516


We study the periapsis shift of a quasi-circular orbit in a general static spherically symmetric spacetime. We derive two formulae in full order with respect to the gravitational field, one in terms of the gravitational mass $m$ and the other in terms of the orbital angular velocity $\omega_{\phi}$. These formulae reproduce the well-known ones for the prograde shift in the Schwarzschild spacetime. In a general case, the shift deviates from that in the Schwarzschild spacetime due to a particular combination of the components of the Ricci tensor at the radius $r$ of the orbit. The formulae give a retrograde shift due to the extended-mass effect in Newtonian gravity. In the post-Newtonian regime of general relativity near a massive compact object, a retrograde shift implies that the energy density is beyond a critical value $\epsilon_{c}=3Gm^{2}/(2\pi r^{4})\simeq 3r^{2}\omega_{\phi}^{4}/(2\pi G)$, whereas a prograde shift greater than that in the Schwarzschild spacetime implies the violation of the weak energy condition there. Implications to the Galactic Centre are also discussed.

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T. Harada, T. Igata, H. Saida, et. al.
Mon, 17 Oct 22
8/56

Comments: 18 pages

On a novel relationship between shear and energy density at the bounce in non-singular Bianchi-I spacetimes [CL]

http://arxiv.org/abs/2210.07257


In classical Bianchi-I spacetimes, underlying conditions for what dictates the singularity structure – whether it is anisotropic shear or energy density, can be easily determined from the generalized Friedmann equation. However, in non-singular bouncing anisotropic models these insights are difficult to obtain in the quantum gravity regime where the singularity is resolved at a non-vanishing mean volume which can be large compared to the Planck volume, depending on the initial conditions. Such non-singular models may also lack a generalized Friedmann equation making the task even more difficult. We address this problem in an effective spacetime description of loop quantum cosmology (LQC) where energy density and anisotropic shear are universally bounded due to quantum geometry effects, but a generalized Friedmann equation has been difficult to derive due to the underlying complexity. Performing extensive numerical simulations of effective Hamiltonian dynamics, we bring to light a surprising, seemingly universal relationship between energy density and anisotropic shear at the bounce in LQC. For a variety of initial conditions for a massless scalar field, an inflationary potential, and two types of ekpyrotic potentials we find that the values of energy density and the anisotropic shear at the quantum bounce follow a novel parabolic relationship which reveals some surprising results about the anisotropic nature of the bounce, such as the maximum value of the anisotropic shear at the bounce is reached when the energy density reaches approximately half of its maximum allowed value. The relationship we find can prove very useful for developing our understanding of the degree of anisotropy of the bounce, isotropization of the post-bounce universe, and discovering the modified generalized Friedmann equation in Bianchi-I models with quantum gravity corrections.

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A. McNamara, S. Saini and P. Singh
Mon, 17 Oct 22
11/56

Comments: 23 pages, 11 figures

BFSS Matrix Model Cosmology: Progress and Challenges [CL]

http://arxiv.org/abs/2210.07288


We review a proposal to obtain an emergent metric space-time and an emergent early universe cosmology from the BFSS matrix model. Some challenges and directions for future research are outlined.

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S. Brahma, R. Brandenberger and S. Laliberte
Mon, 17 Oct 22
12/56

Comments: 7 pages, 1 figure

Observational Constraints on the $f(φ,T)$ gravity theory [CL]

http://arxiv.org/abs/2210.07788


We investigate inflation in modified gravity framework by introducing a direct coupling term between a scalar field $\phi$ and the trace of the energy momentum tensor $T$ as $f(\phi,T) = 2 \phi( \kappa^{1/2} \alpha T + \kappa^{5/2} \beta T^2) $ to the Einstein-Hilbert action. We consider a class of inflaton potentials (i) $V_0 \phi^p e^{-\lambda\phi}$, (ii) $V_0\frac{ \lambda \phi^p}{1+\lambda\phi^p}$ and investigate the sensitivity of the modified gravity parameters $\alpha$ and $\beta$ on the inflaton dynamics. We derive the potential slow-roll parameters, scalar spectral index $n_s$, and tensor-to-scalar ratio $r$ in the above $f(\phi,T)$ gravity theory and analyze the following three choices of modified gravity parameters~(i) Case I:~ $\alpha \neq 0, ~\beta=0$ i.e. neglecting higher order terms, (ii) Case II:~ $\alpha=0$, $\beta \neq 0$~ and do the analysis for $T^2$ term, (iii) Case III:~ $\alpha \neq 0$ and $\beta \neq 0$ i.e. keeping all terms. For a range of potential parameters, we obtain constraints on $\alpha$ and $\beta$ in each of the above three cases using the WMAP and the PLANCK data.

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A. Ashmita, P. Sarkar and P. Das
Mon, 17 Oct 22
14/56

Comments: 15 pages, 6 figures

A combinatorial algebraic approach for the modified second-generation time-delay interferometry [IMA]

http://arxiv.org/abs/2210.07801


We generalize the combinatorial algebraic approach first proposed by Dhurandhar et al. to construct various classes of modified second-generation time-delay interferometry (TDI) solutions. The main idea behind the algorithm is to enumerate, in a given order, a specific type of commutator between two monomials defined by the products of particular time-displacement operators. On the one hand, the above commutators can be systematically rewritten as the elements of a left ideal, defined by the l.h.s. of the relevant equation for the TDI solution. On the other hand, these commutators are shown to vanish if we only keep up the first-order contributions regarding the rate of change of armlengths. In other words, each commutator furnishes a valid TDI solution pertaining to the given type of modified second-generation combinations. In this work, the original algorithm, which only involves time-delay operators, is extended by introducing the time-advance ones and then utilized to seek solutions of the Beacon, Relay, Monitor, Sagnac, and fully symmetric Sagnac types. We discuss the relation between the present scheme’s solutions and those obtained by the geometric TDI approach, a well-known method of exhaustion of virtual optical paths. In particular, we report the results on novel Sagnac-inspired solutions that cannot be straightforwardly obtained using the geometric TDI algorithm. The average response functions, floor noise power spectral densities, and sensitivity functions are evaluated for the obtained solutions.

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Z. Wu, P. Wang, W. Qian, et. al.
Mon, 17 Oct 22
17/56

Comments: N/A

Relativistic Hydrodynamics a brief review of classical and quantum fluids in relativistic astrophysics [CL]

http://arxiv.org/abs/2210.07331


The objective of this work is to revisit fundamental aspects of relativistic hydrodynamics, aiming at the construction of a first course in relativistic hydrodynamics and its applications to astrophysics at the level of end of undergraduate course and beginning of graduate course. We aim to introduce more basic concepts of basic hydrodynamics, going through models analogous to gravity to the theory of superfluids, applying mainly to astrophysics and the cosmology of the dark universe. We review the classical hydrodynamics, Galileo symmetry and its extension to Lorentz Symmetry applied to fluids, enabling the analogy of fluids with space-time. We study the conservation of the momentum-energy tensor and the energy conditions of Hawking-Ellis. In the next sections we investigate quantum effects, in particular linked to superfluids, and we also sketch an application to dark matter. In this study, we conclude that superfluidity is one of the possible ways to quantize gravity.

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R. Santos, A. Jr and L. Almeida
Mon, 17 Oct 22
24/56

Comments: N/A

Gravitational focusing effects on streaming dark matter as a new detection concept [IMA]

http://arxiv.org/abs/2210.07367


This work suggests how to search for streaming constituents from the dark sector. Following cosmological reasoning, a very large number of dark fine grained streams are expected in the Galaxy. Within the solar system, planetary gravitational focusing is effective for the slow DM particles, with possible strong flux enhancements only for streaming dark constituents. The present simulation incorporates gravitational effects preceding their encounter with Earth bound detectors. The gravitational self-focusing by the inner Earth can be large, and therefore must also be taken into account. Spatiotemporal transient density enhancements are also derived, which are of interest for DM experiments. Due to the built-in gravitational flux enhancements, advantages are expected when compared to the detection schemes designed for the smooth Standard Halo Model (SHM). In addition, a network of sensors would have a much better discovery potential as long as the hypothetical streams of dark constituents, along their rest mass and coupling strength to normal matter are unknown. This work is relevant for all ongoing DM searches, including state-of-the-art detection schemes like GNOME, EDM experiments, and the ECHO idea. Also astrophysical searches for the dark sector could benefit more when targeting planetary and solar/stellar atmospheres. The present simulation focuses on fine grained streams but it can be applied to any configuration of invisible matter propagating inside the solar system.

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A. Kryemadhi, M. Maroudas, A. Mastronikolis, et. al.
Mon, 17 Oct 22
31/56

Comments: N/A

Robust Supermassive Black Hole Spin Mass-Energy Characteristics: A New Method and Results [HEAP]

http://arxiv.org/abs/2210.07779


The rotational properties of astrophysical black holes are fundamental quantities that characterization the black holes. A new method to empirically determine the spin mass-energy characteristics of astrophysical black holes is presented and applied here. Results are obtained for a sample of 100 supermassive black holes with collimated dual outflows and redshifts between about zero and two. An analysis indicates that about two-thirds of the black holes are maximally spinning, while one-third have a broad distribution of spin values; it is shown that the same distributions describe the quantity $\rm{(M_{rot}/M_{irr})}$. The new method is applied to obtain the black hole spin mass-energy, $\rm{M_{spin}}$, available for extraction relative to: the maximum possible value, the irreducible black hole mass, and the total black hole mass, $\rm{M_{dyn}}$. The total energy removed from the black hole system and deposited into the circumgalactic medium via dual outflows over the entire outflow lifetime of the source, $\rm{E_T}$, is studied relative to $\rm{M_{dyn}}$ and relative to the spin energy available per black hole, $\rm{E_{spin}/(M_{\odot}c^2)}$. The mean value of $\rm{Log(E_T/M_{dyn})}$ is about $(-2.47\pm 0.27)$. Several explanations of this and related results are discussed. For example, the energy input to the ambient gas from the outflow could turn off the accretion, or the impact of the black hole mass loss on the system could destabilize and terminate the outflow. The small values and restricted range of values of $\rm{Log(E_T/M_{dyn})}$ and $\rm{Log(E_T/E_{spin})}$ could suggest that these are fundamental properties of the primary process responsible for producing the dual collimated outflows.

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R. Daly
Mon, 17 Oct 22
43/56

Comments: 16 pages, 20 figures, 3 tables

Expanding RIFT: Improving performance for GW parameter inference [CL]

http://arxiv.org/abs/2210.07912


The Rapid Iterative FiTting (RIFT) parameter inference algorithm provides a framework for efficient, highly-parallelized parameter inference for GW sources. In this paper, we summarize essential algorithm enhancements and operating point choices for the RIFT iterative algorithm, including choices used for analysis of LIGO/Virgo O3 observations. We also describe other extensions to the RIFT algorithm and software ecosystem. Some extensions increase RIFT’s flexibility to produce outputs pertinent to GW astrophysics. Other extensions increase its computational efficiency or stability. Using many randomly-selected sources, we assess code robustness with two distinct code configurations, one designed to mimic settings as of LIGO O3 and another employing several performance enhancements. We illustrate RIFT’s capabilities with analysis of selected events

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J. Wofford, A. Yelikar, H. Gallagher, et. al.
Mon, 17 Oct 22
50/56

Comments: N/A

Astrophysical searches of ultralight particles [CL]

http://arxiv.org/abs/2210.06837


The Standard Model of particle physics is a $SU(3)_c\times SU(2)_L\times U(1)_Y$ gauge theory that can explain the strong, weak, and electromagnetic interactions between the particles. The gravitational interaction is described by Einstein’s General Relativity theory which is a classical theory of gravity. These theories can explain all the four fundamental forces of nature with great level of accuracy. However, there are several theoretical and experimental motivations of studying physics beyond the Standard Model of particle physics and Einstein’s General Relativity theory. Probing these new physics scenarios with ultralight particles has its own importance as they can be a promising candidates for dark matter that can evade the constraints from dark matter direct detection experiments and solve the small scale structure problems of the universe. In this paper, we have considered axions and gauge bosons as light particles and their possible searches through astrophysical observations. In particular, we obtain constraints on ultralight axions from orbital period loss of compact binary systems, gravitational light bending, and Shapiro time delay. We also derive constraints on ultralight gauge bosons from indirect evidence of gravitational waves, and perihelion precession of planets. Such type of observations can also constrain several particle physics models and are discussed.

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T. Poddar
Fri, 14 Oct 22
2/75

Comments: 6 pages, 3 figures, 3 tables, proceedings for 41st International Conference on High Energy Physics – ICHEP2022

Determining the spin of light primordial black holes with Hawking radiation [CL]

http://arxiv.org/abs/2210.06500


We propose a method to determine the mass and spin of primordial black holes (PBHs) in the mass range $5\times 10^7-10^{12}$ kg (Hawking temperatures $\sim10$ MeV $-200$ GeV), based on measuring the energy of specific features in the photon Hawking emission spectrum, including both primary and secondary components. This is motivated by scenarios where PBHs in this mass range spin up as they evaporate, namely the string axiverse, where dimensionless spin parameters $\tilde{a}\sim 0.1-0.5$ can be achieved through the Hawking emission of hundreds or even thousands of light axion-like particles. Measuring the present PBH mass-spin distribution may thus be an important probe of physics beyond the Standard Model. Since the proposed method relies on the energy of the photons emitted by a given PBH, rather than on the associated flux, it is independent of the PBH-Earth distance and, as a byproduct, can also be used to infer the latter.

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M. Calzà and J. Rosa
Fri, 14 Oct 22
16/75

Comments: 19 pages, 13 figures

Optical measurement of superluminal motion in the neutron-star merger GW170817 [HEAP]

http://arxiv.org/abs/2210.06568


The afterglow of the binary neutron star merger GW170817 gave evidence for a structured relativistic jet and a link between such mergers and short gamma-ray bursts. Superluminal motion, found using radio very long baseline interferometry (VLBI), together with the afterglow light curve provided constraints on the viewing angle (14-28 degrees), the opening angle of the jet core (less than about 5 degrees), and a modest limit on the initial Lorentz factor of the jet core (more than 4). Here we report on another superluminal motion measurement, at seven times the speed of light, leveraging Hubble Space Telescope precision astrometry and previous radio VLBI data of GW170817. We thereby obtain a unique measurement of the Lorentz factor of the wing of the structured jet, as well as substantially improved constraints on the viewing angle (19-25 degrees) and the initial Lorentz factor of the jet core (more than 40).

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K. Mooley, J. Anderson and W. Lu
Fri, 14 Oct 22
22/75

Comments: Published in Nature main journal (full-text SharedIt link: this https URL). Jet proper motion data available at: this https URL and this http URL

Super-horizon resonant magnetogenesis during inflation [CEA]

http://arxiv.org/abs/2210.07050


We propose a novel mechanism for significantly enhancing the amplitude of primordial electromagnetic fields during inflation. Similar to existing proposals, our idea is based on parametric resonance effects due to conformal-symmetry-breaking coupling of the gauge field and the inflaton. Our proposed scenario, however, significantly differs from previously studied models, and avoids their shortcomings. We, particularly, construct a viable system where the gauge field is exponentially amplified on super-horizon scales, therefore evading the no-go theorem formulated on the basis of widely encountered drastic back-reaction of the magnetic field energy on the inflationary background. We compute the spectrum of the produced magnetic fields and demonstrate the compatibility with current observational constraints.

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M. Sasaki, V. Vardanyan and V. Yingcharoenrat
Fri, 14 Oct 22
32/75

Comments: 10 pages, 6 figures

Probing the interaction between dark energy and dark matter with future fast radio burst observations [CEA]

http://arxiv.org/abs/2210.07162


Interacting dark energy (IDE) scenario assumes that there exists a direct interaction between dark energy and cold dark matter, but this interaction is hard to be tightly constrained by the current data. Finding new cosmological probes to precisely measure this interaction could deepen our understanding of dark energy and dark matter. Fast radio bursts (FRBs) will be seen in large numbers by future radio telescopes, and thus they have potential to become a promising low-redshift cosmological probe. In this work, we investigate the capability of future FRBs of constraining the dimensionless coupling parameter $\beta$ in four phenomenological IDE models. We find that in the IDE models with the interaction proportional to the energy density of dark energy, about $10^5$ FRB data can give constraint on $\beta$ tighter than the current cosmic microwave background data. In all the IDE models, about $10^6$ FRB data can constrain the absolute errors of $\beta$ to less than $0.10$, providing a way to precisely measure $\beta$ by only one cosmological probe. The reconstruction of the interaction term also shows that the FRB data could help constrain the redshift evolution of interaction.

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Z. Zhao, L. Wang, J. Zhang, et. al.
Fri, 14 Oct 22
33/75

Comments: 16 pages, 6 figures

Back to the features: assessing the discriminating power of future CMB missions on inflationary models [CEA]

http://arxiv.org/abs/2210.07028


Future Cosmic Microwave Background (CMB) experiments will deliver extremely accurate measurements of the E-modes pattern of the CMB polarization field. Given the sharpness of the E-modes transfer functions, such surveys make for a powerful detector of high-frequency signals from primordial features that may be lurking in current data sets. With a handful of toy models that increase the fit to the latest Planck data, but are of marginal statistical significance, we use a state-of-the-art forecast pipeline to illustrate the promising prospects to test primordial features in the next decade. Not only will future experiments allow us to detect such features in data, but they will also be able to discriminate between models and narrow down the physical mechanism originating them with high statistical significance. On the other hand, if the anomalies in the currently measured CMB spectra are just statistical fluctuations, all the current feature best fit candidates will be ruled out. Either way, our results show that primordial features are a clear target of forthcoming CMB surveys beyond the detection of tensor modes.

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M. Braglia, X. Chen, D. Hazra, et. al.
Fri, 14 Oct 22
37/75

Comments: 36 pages, 15 figures

3XMM J185246.6+003317: an isolated massive neutron star with a low magnetic field and a carbon atmosphere [HEAP]

http://arxiv.org/abs/2210.06648


3XMM J185246.6+003317 is a slowly rotating soft-gamma repeater (neutron star) in the vicinity of the supernova remnant Kes\,79. So far, observations have only set upper limits to its surface magnetic field and spindown, and there is no estimate for its mass and radius. Using ray-tracing modelling and Bayesian inference for the analysis of several light curves spanning a period of around three weeks, we have found that it may be one of the most massive neutron stars to date. In addition, our analysis suggests a multipolar magnetic field structure with a subcritical field strength and a carbon atmosphere composition. Due to the time-resolution limitation of the available light curves, we estimate the surface magnetic field and the mass to be $\log_{10} (B/{\rm G}) = 11.89^{+0.19}{-0.93}$ and $M=2.09^{+0.16}{-0.09}$~$M_{\odot}$ at $1\sigma$ confidence level, while the radius is estimated to be $R=12.02^{+1.44}_{-1.42}$ km at $2\sigma$ confidence level. The robustness of these estimates was verified by simulations, i.e., data injections with known model parameters, and their subsequent recovery. The best-fit model has three small hot spots, two of them in the southern hemisphere. We interpret the above results as due to accretion of supernova layers/interstellar medium onto 3XMM J185246.6+003317 leading to burying and a subsequent re-emergence of the magnetic field, and a carbon atmosphere being formed possibly due to hydrogen/helium diffusive nuclear burning. Finally, we briefly discuss some consequences of our findings for superdense matter constraints.

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R. Lima, J. Pereira, J. Coelho, et. al.
Fri, 14 Oct 22
46/75

Comments: 23 pages, 10 figures, 2 tables. Comments welcome

Lifetime of scalar cloud formation around a rotating regular black hole [CL]

http://arxiv.org/abs/2210.06861


Does circumventing the curvature singularity of the Kerr black hole affects the timescale of the scalar cloud formation around it? By definition, the scalar cloud, forms a gravitational atom with hydrogen-like bound states, lying on the threshold of a massive scalar field’s superradiant instability regime (time-growing quasi-bound states) and beyond (time-decaying quasi-bound states). By taking a novel type of rotating hollow regular black hole proposed by Simpson and Visser which unlike its standard rivals has an asymptotically Minkowski core, we address this question. The metric has a minimal extension relative to the standard Kerr, originating from a single regularization parameter $\ell$, with length dimension. We show with the inclusion of the regularization length scale $\ell$ into the Kerr spacetime, without affecting the standard superradiant instability regime, the timescale of scalar cloud formation gets shorter. Since the scalar cloud after its formation, via energy dissipation, can play the role of a continuum source for gravitational waves, such a reduction in the instability growth time improves the phenomenological detection prospects of new physics because the shorter the time, the more astrophysically important.

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M. Khodadi and R. Pourkhodabakhshi
Fri, 14 Oct 22
48/75

Comments: 13 pages (two column), 6 figures, 1 table

Minisuperspace Quantum Cosmology from the Einstein-Cartan Path Integral [CL]

http://arxiv.org/abs/2210.05583


We derive the fixed-$\Lambda$ and unimodular propagators using the path integral formalism as applied to the Einstein-Cartan action. The simplicity of the action (which is linear in the lapse function) allows for an exact integration starting from the lapse function and the enforcement of the Hamiltonian constraint, leading to a product of Chern-Simons states if the connection is fixed at the endpoints. No saddle point approximation is needed. Should the metric be fixed at the endpoints, then, depending on the contour chosen for the connection, Hartle-Hawking or Vilenkin propagators are obtained. Thus, in this approach one trades a choice of contour in the lapse function for one in the connection, where appropriate. The unimodular propagators are also trivial to obtain via the path integral, and the previously derived expressions are recovered.

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R. Isichei and J. Magueijo
Fri, 14 Oct 22
51/75

Comments: N/A

Modified gravity approaches to the cosmological constant problem [CL]

http://arxiv.org/abs/2210.06810


The cosmological constant and its phenomenology remain among the greatest puzzles in theoretical physics. We review how modifications of Einstein’s general relativity could alleviate the different problems associated with it that result from the interplay of classical gravity and quantum field theory. We introduce a modern and concise language to describe the problems associated with its phenomenology, and inspect no-go theorems and their loopholes to motivate the approaches discussed here. Constrained gravity approaches exploit minimal departures from general relativity; massive gravity introduces mass to the graviton; Horndeski theories lead to the breaking of translational invariance of the vacuum; and models with extra dimensions change the symmetries of the vacuum. We also review screening mechanisms that have to be present in some of these theories if they aim to recover the success of general relativity on small scales as well. Finally, we summarise the statuses of these models in their attempt to solve the different cosmological constant problems while being able to account for current astrophysical and cosmological observations.

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F. Collaboration, H. Bernardo, B. Bose, et. al.
Fri, 14 Oct 22
55/75

Comments: 54 pages, 2 figures, 1 table. Invited review for Universe, Special Issue “Cosmological Constant” (this https URL)

Solar System-scale interferometry on fast radio bursts could measure cosmic distances with sub-percent precision [CEA]

http://arxiv.org/abs/2210.07159


The light from a source at a distance d will arrive at detectors separated by 100 AU at times that differ by as much as 120 (d/100 Mpc)^{-1} nanoseconds because of the curvature of the wavefront. At gigahertz frequencies, the arrival time difference can be determined to better than a nanosecond with interferometry. If the space-time positions of the detectors are known to a few centimeters, comparable to the accuracy to which very long baseline interferometry baselines and global navigation satellite systems (GNSS) geolocations are constrained, nanosecond timing would allow competitive cosmological constraints. We show that a four-detector constellation at Solar radii of >10 AU could measure distances to individual sources with sub-percent precision and, hence, cosmological parameters such as the Hubble constant to this precision. FRBs are the only known bright extragalactic radio source that are sufficiently point-like. Galactic scattering limits the timing precision at <5 GHz, whereas at higher frequencies the precision is set by removing dispersion. Furthermore, for baselines greater than 100 AU, Shapiro time delays limit the precision, but their effect can be cleaned with two additional detectors. Accelerations that result in ~1 cm uncertainty in detector positions (from variations in the Sun’s irradiance, dust collisions and gaseous drag) could be corrected for with weekly GNSS-like trilaterations. Gravitational accelerations from asteroids occur over longer timescales, and so a setup with a precise accelerometer and calibrating the space-time detector positions off of distant FRBs may also be sufficient. The proposed interferometer would also resolve the radio emission region of Galactic pulsars, constrain the mass distribution in the outer Solar System, and reach interesting sensitivities to ~0.01-100 micro-Hz gravitational waves.

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K. Boone and M. McQuinn
Fri, 14 Oct 22
57/75

Comments: 34 pages in preprint format; 3 figures; to be submitted to JCAP; comments welcome!

Effective dark energy through spin-gravity coupling [CL]

http://arxiv.org/abs/2210.06598


We investigate cosmological scenarios with spin-gravity coupling. In particular, due to the spin of the baryonic and dark matter particles and its coupling to gravity, they probe an effective spin-dependent metric, which can be calculated semi-classically in the Mathisson-Papapetrou-Tulczyjew-Dixon formalism. Hence, the usual field equations give rise to modified Friedmann equations, in which the extra terms can be identified as an effective dark-energy sector. Additionally, we obtain an effective interaction between the matter and dark-energy sectors. In the case where the spin-gravity coupling switches off, we recover standard $\Lambda$CDM cosmology. We perform a dynamical system analysis and we find a matter-dominated point that can describe the matter era, and a stable late-time solution corresponding to acceleration and dark-energy domination. For small values of the spin coupling parameter, deviations from $\Lambda$CDM concordance scenario are small, however for larger values they can be brought to the desired amount, leading to different dark-energy equation-of-state parameter behavior, as well as to different transition redshift from acceleration to deceleration. Finally, we confront the model predictions with Hubble function data.

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G. Otalora and E. Saridakis
Fri, 14 Oct 22
63/75

Comments: 7 pages, 4 figures

Lorentz invariance violation induced threshold anomaly versus very-high energy cosmic photon emission from GRB20221009A [HEAP]

http://arxiv.org/abs/2210.06338


It is reported that the Large High Altitude Air Shower Observatory (LHAASO) observed very high energy photons from GRB 20221009A, with the highest energy reaching 18 TeV. We find that observation of such high energy photons is a quite nontrivial fact since extragalactic background light could absorb these photons severely and the flux is too weak to be observed. Therefore we discuss the potential new mechanism for us to observe these photons, and suggest that Lorentz invariance violation induced threshold anomaly of the process (\gamma\gamma\to e^-e^+) provides a candidate to explain this phenomenon.

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H. Li and B. Ma
Thu, 13 Oct 22
2/68

Comments: 4 latex pages, 2 figures

Recoil Velocity of Binary Neutron Star Merger Remnants [HEAP]

http://arxiv.org/abs/2210.06357


The LIGO-Virgo gravitational wave detectors have confidently observed 4 events involving neutron stars: two binary neutron star (BNS) mergers (GW170817 and GW190425), and two neutron star-black hole mergers (GW200105 and GW200115). However, our theoretical understanding of the remnant properties of such systems is incomplete due to the complexities related to the modeling of matter effects and the very high computational cost of corresponding numerical relativity simulations. An important such property is the recoil velocity, which is imparted onto the remnant due to the anisotropic emission of gravitational radiation and the dynamical ejection of matter in the kilonova. In this work, we combine gravitational radiation as well as dynamical ejecta distributions, computed by the Computational Relativity numerical simulations, to get accurate estimates for BNS remnant recoil velocities. We find that recoils due to ejection of matter dominate those caused by gravitational wave emission. Knowledge of BNS remnant recoil velocities is important in determining if the remnant is retained by its environment for future hierarchical mergers which, in turn, can form binaries with black holes in the so-called lower mass gap of 3 to 5 solar masses.

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S. Kulkarni, S. Padamata and A. Gupta
Thu, 13 Oct 22
12/68

Comments: 5 pages, 2 figures, submitted to Proc. of IAU Symp. 363

Neural Importance Sampling for Rapid and Reliable Gravitational-Wave Inference [CL]

http://arxiv.org/abs/2210.05686


We combine amortized neural posterior estimation with importance sampling for fast and accurate gravitational-wave inference. We first generate a rapid proposal for the Bayesian posterior using neural networks, and then attach importance weights based on the underlying likelihood and prior. This provides (1) a corrected posterior free from network inaccuracies, (2) a performance diagnostic (the sample efficiency) for assessing the proposal and identifying failure cases, and (3) an unbiased estimate of the Bayesian evidence. By establishing this independent verification and correction mechanism we address some of the most frequent criticisms against deep learning for scientific inference. We carry out a large study analyzing 42 binary black hole mergers observed by LIGO and Virgo with the SEOBNRv4PHM and IMRPhenomXPHM waveform models. This shows a median sample efficiency of $\approx 10\%$ (two orders-of-magnitude better than standard samplers) as well as a ten-fold reduction in the statistical uncertainty in the log evidence. Given these advantages, we expect a significant impact on gravitational-wave inference, and for this approach to serve as a paradigm for harnessing deep learning methods in scientific applications.

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M. Dax, S. Green, J. Gair, et. al.
Thu, 13 Oct 22
13/68

Comments: 7+7 pages, 1+5 figures

Fifth forces and frame invariance [CL]

http://arxiv.org/abs/2210.06396


I discuss how one can apply the covariant formalism developed by Vilkovisky and DeWitt to obtain frame invariant fifth force calculations for scalar-tensor theories. Fifth forces are severely constrained by astrophysical measurements. It was shown previously that for scale-invariant Higgs-dilaton gravity, in a particular choice of Jordan frame, the dilaton fifth force is dramatically suppressed, evading the observational constraints. Using a geometric approach I extend this result to all frames, and show that the usual dichotomy of “Jordan frame” versus “Einstein frame” is better understood as a continuum of frames: submanifold slices of a more general field space.

Read this paper on arXiv…

J. Bamber
Thu, 13 Oct 22
18/68

Comments: 12 pages, 1 figure