Return of Harrison-Zeldovich spectrum in light of recent cosmological tensions [CEA]

http://arxiv.org/abs/2210.06125


The spectral index $n_s$ of scalar perturbation is the significant initial condition set by inflation theory for our observable Universe. According to Planck results, current constraint is $n_s = 0.965\pm 0.004$, while an exact scale-invaiant Harrison-Zeldovich spectrum, i.e. $n_s=1$, has been ruled out at $8.4\sigma$ significance level. However, it is well-known that the standard $\Lambda$CDM model is suffering from the Hubble tension, which is at $\sim 5\sigma$ significance level. This inconsistency likely indicates that the comoving sound horizon at last scattering surface is actually lower than expected, which so seems to be calling for the return of $n_s=1$. Here, in light of recent observations we find strong evidence for a $n_s=1$ Universe. And we show that if so, it would be confirmed conclusively by CMB-S4 experiment.

Read this paper on arXiv…

J. Jiang, G. Ye and Y. Piao
Thu, 13 Oct 22
22/68

Comments: 21 pages, 5 figures

Cornering Extended Starobinsky Inflation with CMB and SKA [CEA]

http://arxiv.org/abs/2210.05698


Starobinsky inflation is an attractive, fundamental model to explain the Planck measurements, and its higher-order extension may allow us to probe quantum gravity effects. We show that future CMB data combined with the 21cm intensity map from SKA will meaningfully probe such an extended Starobinsky model. A combined analysis will provide a precise measurement and intriguing insight into inflationary dynamics, even accounting for correlations with astrophysical parameters.

Read this paper on arXiv…

T. Modak, L. Röver, B. Schäfer, et. al.
Thu, 13 Oct 22
25/68

Comments: 26 pages, 7 figures

GWSim: A python package to create GW mock samples for different astrophysical populations and cosmological models of binary black holes [CEA]

http://arxiv.org/abs/2210.05724


Precision cosmology with gravitational wave (GW) sources requires understanding the interplay between GW source population and cosmological parameters governing the dynamics of the Universe. With the fast increase of GW detections, for exploring many aspects of cosmology and fundamental physics it is necessary to develop a tool which can simulate GW mock samples for several population and cosmological models with and without a galaxy catalog. We have developed a new code called GWSim, allowing to make GW mock events from a large range of configurations, varying the cosmology, the merger rate, and the GW source parameters (mass and spin distributions in particular), for a given network of GW detectors. We restrict the cosmology to spatially flat universes, including models with varying dark energy equation of state. GWSim provides each mock event with a position in the sky and a redshift; these values can be those of random host galaxies coming from an isotropic and homogeneous simulated Universe or a user-supplied galaxy catalog. We use realistic detector configurations of the LIGO and Virgo network of detectors to show the performance of this code for the latest observation runs and the upcoming observation run.

Read this paper on arXiv…

C. Karathanasis, B. Revenu, S. Mukherjee, et. al.
Thu, 13 Oct 22
28/68

Comments: 18 pages, 13 figures, Prepared for submission to A&A

Asymptotic Green's function solutions of the general relativistic thin disc equations [CL]

http://arxiv.org/abs/2210.06161


The leading order Green’s function solutions of the general relativistic thin disc equations are computed, using a pseudo-Newtonian potential and asymptotic Laplace mode matching techniques. This solution, valid for a vanishing ISCO stress, is constructed by ensuring that it reproduces the leading order asymptotic behaviour of the near-ISCO, Newtonian, and global WKB limits. Despite the simplifications used in constructing this solution, it is typically accurate, for all values of the Kerr spin parameter $a$ and at all radii, to less than a percent of the full numerically calculated solutions of the general relativistic disc equations. These solutions will be of use in studying time-dependent accretion discs surrounding Kerr black holes.

Read this paper on arXiv…

A. Mummery
Thu, 13 Oct 22
34/68

Comments: 9 pages, 7 figures, 4 appendices. Accepted for publication in MNRAS

Multi-messenger constraints on Abelian-Higgs cosmic string networks [CEA]

http://arxiv.org/abs/2210.06178


Nielsen-Olesen vortices in the Abelian-Higgs (AH) model are the simplest realisations of cosmic strings in a gauge field theory. Large-scale numerical solutions show that the dominant decay channel of a network of AH strings produced from random initial conditions is classical field radiation. However, they also show that with special initial conditions, loops of string can be created for which classical field radiation is suppressed, and which behave like Nambu-Goto (NG) strings with a dominant decay channel into gravitational radiation. This indicates that cosmic strings are generically sources of both high-energy particles and gravitational waves. Here we adopt a simple parametrisation of the AH string network allowing for both particle and gravitational wave production, which sets the basis for a “multi-messenger” investigation of this model. We find that, in order to explain the NANOGrav detection of a possible gravitational wave background, while satisfying the constraint on NG-like loop production from simulations and bounds from the cosmic microwave background, the tension of the AH string in Planck units $G\mu$ and the fraction of the NG-like loops $f_{\rm NG}$ should satisfy $G\mu f_{\rm NG}^{2.6} \gtrsim 3.2\times 10^{-13}$ at 95$\%$ confidence. On the other hand, for such string tensions, constraints from the diffuse gamma-ray background (DGRB) indicate that more than 97$\%$ of the total network energy should be converted to dark matter (DM) or dark radiation. We also consider joint constraints on the annihilation cross-section, the mass, and the relic abundance of DM produced by decays of strings. For example, for a DM mass of 500 GeV, the observed relic abundance can be explained by decaying AH strings that also account for the NANOGrav signal.

Read this paper on arXiv…

M. Hindmarsh and J. Kume
Thu, 13 Oct 22
38/68

Comments: 20 pages, 4 figures

Quantum Modified Gravity at Low Energy in the Ricci Flow of Quantum Spacetime [CL]

http://arxiv.org/abs/2210.06082


Quantum treatment of physical reference frame leads to the Ricci flow of quantum spacetime, which is a quite rigid framework to quantum and renormalization effect of gravity. The theory has a low characteristic energy scale described by a unique constant: the critical density of the universe. At low energy long distance (cosmic or galactic) scale, the theory modifies Einstein’s gravity which naturally gives rise to a cosmological constant as a counter term of the Ricci flow at leading order and an effective scale dependent Einstein-Hilbert action.
In the weak and static gravity limit, the framework naturally contains a MOdified Newtonian Dynamics (MOND)-like theory first proposed by Milgrom. When local curvature is large, Newtonian gravity is recovered. When local curvature is lower or comparable with the asymptotic background curvature corresponding to the characteristic energy scale, the baryonic Tully-Fisher relation can be obtained. For intermediate general curvature, the interpolating Lagrangian function gives a similar curve to the observed radial acceleration relation of galaxies.
The critical acceleration constant $a_{0}$ introduced in MOND is related to the low characteristic energy scale of the theory. The cosmological constant gives a universal leading order contribution to $a_{0}$ and the flow effect gives the next order scale dependent contribution beyond MOND, which equivalently induces the “cold dark matter” to the theory. $a_{0}$ is consistent with galaxian data when the “dark matter” is about 5 times the baryonic matter. The Ricci flow of quantum spacetime is proposed as a possible underlying theory of MOND and related acceleration discrepancy phenomenon at long distance scale.

Read this paper on arXiv…

M. M.J.Luo
Thu, 13 Oct 22
41/68

Comments: 13 pages

Constraining gravity with synergies between radio and optical cosmological surveys [CEA]

http://arxiv.org/abs/2210.05705


In this work we present updated forecasts on parameterised modifications of gravity that can capture deviations of the behaviour of cosmological density perturbations beyond $\Lambda$CDM. For these forecasts we adopt the SKA Observatory (SKAO) as a benchmark for future cosmological surveys at radio frequencies, combining a continuum survey for weak lensing and angular galaxy clustering with an HI galaxy survey for spectroscopic galaxy clustering that can detect baryon acoustic oscillations and redshift space distortions. Moreover, we also add 21cm HI intensity mapping, which provides invaluable information at higher redshifts, and can complement tomographic resolution, thus allowing us to probe redshift-dependent deviations of modified gravity models. For some of these cases, we combine the probes with other optical surveys, such as the Dark Energy Spectroscopic Instrument (DESI) and the Vera C. Rubin Observatory (VRO). We show that such synergies are powerful tools to remove systematic effects and degeneracies in the non-linear and small-scale modelling of the observables. Overall, we find that the combination of all SKAO radio probes will have the ability to constrain the present value of the functions parameterising deviations from $\Lambda$CDM ($\mu$ and $\Sigma$) with a precision of $2.7\%$ and $1.8\%$ respectively, competitive with the constraints expected from optical surveys and with constraints we have on gravitational interactions in the standard model. Exploring the radio-optical synergies, we find that the combination of VRO with SKAO can yield extremely tight constraints on $\mu$ and $\Sigma$ ($0.9\%$ and $0.7\%$ respectively), which are further improved when the cross-correlation between intensity mapping and DESI galaxies is included.

Read this paper on arXiv…

S. Casas, I. Carucci, V. Pettorino, et. al.
Thu, 13 Oct 22
46/68

Comments: 24 pages, 10 figures

The Eccentricity Distribution of Wide Binaries [SSA]

http://arxiv.org/abs/2210.06429


Future Gaia and Legacy Survey of Space and Time data releases, together with wide area spectroscopic surveys, will deliver large samples of resolved binary stars with phase space coordinates, albeit with low-cadence. Given an eccentricity law $f(\epsilon)$, we derive properties of (i) the velocity distribution $v/\sqrt{G M/r}$ normalised by the value for a circular orbit at the measured separation $r$; (ii) the astrometric acceleration distributions $a/\left(G M/r^2\right)$ again normalised to the circular orbit value. Our formulation yields analytic predictions for the full statistical distribution for some commonly used eccentricity laws, if the timescale of data-sampling is comparable to or exceeds the binary period. In particular, the velocity distribution for the linear eccentricity law is surprisingly simple. With Bayesian analysis, we suggest a method to infer the eccentricity distribution based on the measured velocity distribution.

Read this paper on arXiv…

D. Benisty, N. Evans and A. Davis
Thu, 13 Oct 22
52/68

Comments: 6 figures; 6 pages

A general relativistic extension to mesh-free methods for hydrodynamics [CL]

http://arxiv.org/abs/2210.05682


The detection of gravitational waves has opened a new era for astronomy, allowing for the combined use of gravitational wave and electromagnetic emissions to directly probe the physics of compact objects, still poorly understood. So far, the theoretical modelling of these sources has mainly relied on standard numerical techniques as grid-based methods or smoothed particle hydrodynamics, with only a few recent attempts at using new techniques as moving-mesh schemes. Here, we introduce a general relativistic extension to the mesh-less hydrodynamic schemes in the code GIZMO, which benefits from the use of Riemann solvers and at the same time perfectly conserves angular momentum thanks to a generalised leap-frog integration scheme. We benchmark our implementation against many standard tests for relativistic hydrodynamics, either in one or three dimensions, and also test the ability to preserve the equilibrium solution of a Tolman-Oppenheimer-Volkoff compact star. In all the presented tests, the code performs extremely well, at a level at least comparable to other numerical techniques.

Read this paper on arXiv…

A. Lupi
Thu, 13 Oct 22
61/68

Comments: 16 pages, 14 figures, submitted to MNRAS

General relativistic simulations of collapsing binary neutron star mergers with Monte-Carlo neutrino transport [HEAP]

http://arxiv.org/abs/2210.05670


Recent gravitational wave observations of neutron star-neutron star and neutron star-black hole binaries appear to indicate that massive neutron stars may not be too uncommon in merging systems. These discoveries have led to an increased interest in the simulation of merging compact binaries involving massive stars. In this manuscript, we present a first set of evolution of massive neutron star binaries using Monte-Carlo radiation transport for the evolution of neutrinos. We study a range of systems, from nearly symmetric binaries that collapse to a black hole before forming a disk or ejecting material, to more asymmetric binaries in which tidal disruption of the lower mass star leads to the production of more interesting post-merger remnants. For the latter type of systems, we additionally study the impact of viscosity on the properties of the outflows, and compare our results to two recent simulations of identical binaries performed with the WhiskyTHC code. We find excellent agreement on the black hole properties, disk mass, and mass and velocity of the outflows, and some minor but noticeable differences in the evolution of the electron fraction when using a subgrid viscosity model. The method used to account for r-process heating in the determination of the outflow properties appears to have a larger impact on our result than those differences between numerical codes. We also take advantage of the use of a Monte-Carlo code to study in more detail the neutrino energy spectrum, and use the simulation with the most ejected material to verify that our newly implemented Lagrangian tracers provide a reasonable sampling of the matter outflows as they leave the computational grid.

Read this paper on arXiv…

F. Foucart, M. Duez, R. Haas, et. al.
Wed, 12 Oct 22
12/75

Comments: 18p, 9 figures, to be submitted to PRD

Cosmological-model-independent determination of Hubble constant from fast radio bursts and Hubble parameter measurements [CEA]

http://arxiv.org/abs/2210.05202


We establish a new cosmological-model-independent method to determine the Hubble constant $H_0$ from the localized FRBs and the Hubble parameter measurements and obtain a first such determination $H_0=70.60\pm2.11~\mathrm{km/s/Mpc}$ of about 3.00\% uncertainty with data from the eighteen localized FRBs and nineteen Hubble parameter measurements in the redshift range $0<z\leq0.66$. This value, which is independent of the cosmological model, lies in the middle of the results from the Planck CMB observations and the nearby type Ia supernovae (SN Ia) data. Simulations show that the uncertainty of $H_0$ can be decreased to the level of that from the nearby SN Ia when mock data from 500 localized FRBs with 25 Hubble parameter in the redshift range of $0<z\leq1$ are used. Since localized FRBs are expected to be detected in large quantities, our method will be able to give a reliable and more precise determination of $H_0$ in the very near future, which will help us to figure out the possible origin of the Hubble constant tension.

Read this paper on arXiv…

Y. Liu, H. Yu and P. Wu
Wed, 12 Oct 22
27/75

Comments: 12 pages, 2 figures

Lensing of gravitational waves: efficient wave-optics methods and validation with symmetric lenses [CL]

http://arxiv.org/abs/2210.05658


Gravitational wave (GW) astronomy offers the potential to probe the wave-optics regime of gravitational lensing. Wave optics (WO) effects are relevant at low frequencies, when the wavelength is comparable to the characteristic lensing time delay multiplied by the speed of light, and are thus often negligible for electromagnetic signals. Accurate predictions require computing the conditionally convergent diffraction integral, which involves highly oscillatory integrands and is numerically difficult. We develop and implement several methods to compute lensing predictions in the WO regime valid for general gravitational lenses. First, we derive approximations for high and low frequencies, obtaining explicit expressions for several analytic lens models. Next, we discuss two numerical methods suitable in the intermediate frequency range: 1) Regularized contour flow yields accurate answers in a fraction of a second for a broad range of frequencies. 2) Complex deformation is slower, but requires no knowledge of solutions to the geometric lens equation. Both methods are independent and complement each other. We verify sub-percent accuracy for several lens models, which should be sufficient for applications to GW astronomy in the near future. Apart from modelling lensed GWs, our method will also be applicable to the study of plasma lensing of radio waves and tests of gravity.

Read this paper on arXiv…

G. Tambalo, M. Zumalacárregui, L. Dai, et. al.
Wed, 12 Oct 22
39/75

Comments: 19 pages, 8 figures

Three-dimensional core-collapse supernovae with complex magnetic structures: II. Rotational instabilities and multimessenger signatures [HEAP]

http://arxiv.org/abs/2210.05012


The gravitational collapse of rapidly rotating massive stars can lead to the onset of the low $T/|W|$ instability within the central proto-neutron star (PNS), which leaves strong signatures in both the gravitational wave (GW) and neutrino emission. Strong large-scale magnetic fields are usually invoked to explain outstanding stellar explosions of rapidly rotating progenitors, but their impact on the growth of such instability has not yet been cleared. We analyze a series of three-dimensional magnetohydrodynamic models to characterize the effects of different magnetic configurations on the development of the low $T/|W|$ and the related multi-messenger features. In the absence of magnetic fields, we observe the growth on dynamical time scales of the low $T/|W|$, associated with a strong burst of GW and a correlated modulation of the neutrino emission. However, models with a strong magnetic field show a quenching of the low $T/|W|$, due to a flattening of the rotation profile in the first $\sim100$ ms after shock formation caused by the magnetic transport of angular momentum. The associated GW emission is weakened by an order of magnitude, exhibits a broader spectral shape, and has no dominant feature associated with the PNS large-scale oscillation modes. Neutrino luminosities are damped along the equatorial plane due to a more oblate PNS, and the only clear modulation in the signal is due to SASI activity. Finally, magnetized models produce lower luminosities for $\nu_e$ than for $\bar{\nu}_e$, which is connected to a higher concentration of neutron-rich material in the PNS surroundings.

Read this paper on arXiv…

M. Bugli, J. Guilet, T. Foglizzo, et. al.
Wed, 12 Oct 22
47/75

Comments: 13 pages, 17 figures; submitted to MNRAS

Polarized primordial gravitational waves in spatial covariant gravities [CL]

http://arxiv.org/abs/2210.05259


The spatial covariant gravities provide a natural way to including odd-order spatial derivative terms into the gravitational action, which breaks the parity symmetry at gravitational sector. A lot of parity-violating scalar-tensor theories can be mapped to the spatial covariant framework by imposing the unitary gauge. This provides us a general framework for exploring the parity-violating effects in the primordial gravitational waves (PGWs). The main purpose of this paper is to investigate the polarization of PGWs in the spatial covariant gravities and their possible observational effects. To this end, we first construct the approximate analytical solution to the mode function of the PGWs during the slow-roll inflation by using the uniform asymptotic approximation. With the approximate solution, we calculate explicitly the power spectrum and the corresponding circular polarization of the PGWs analytically. It is shown that the new contributions to power spectrum from spatial covariant gravities contain two parts, one from the parity-preserving terms and the other from the parity-violating terms. While the parity-preserving terms can only affect the overall amplitudes of PGWs, the parity-violating terms induce nonzero circular polarization of PGWs, i.e., the left-hand and right-hand polarization modes of GWs have different amplitudes. The observational implications of this nonzero circular polarization is also briefly discussed.

Read this paper on arXiv…

T. Zhu, W. Zhao and A. Wang
Wed, 12 Oct 22
61/75

Comments: 11 pages. arXiv admin note: text overlap with arXiv:1911.01580

Testing Gravity with Black Hole X-Ray Data [CL]

http://arxiv.org/abs/2210.05322


The analysis of the properties of the X-ray radiation emitted from geometrically thin accretion disks around black holes can be a powerful tool to test General Relativity in the strong field regime. This chapter reviews the state-of-the-art of gravity tests with black hole X-ray data. So far, most efforts have been devoted to test the Kerr hypothesis – namely that the spacetime around astrophysical black holes is described by the Kerr solution – and X-ray data can currently provide among the most stringent constraints on possible deviations from the Kerr geometry. As of now, all X-ray analyses are consistent with the predictions of General Relativity.

Read this paper on arXiv…

C. Bambi
Wed, 12 Oct 22
65/75

Comments: 35 pages, 13 figures. Chapter for the book “Recent Progress on Gravity Tests” (Eds. C. Bambi and A. C\’ardenas-Avenda\~no, Springer Singapore, expected in 2023). It reviews current X-ray constraints on the Kerr hypothesis and discusses the systematic uncertainties

Constraints on the contributions to the observed binary black hole population from individual evolutionary pathways in isolated binary evolution [HEAP]

http://arxiv.org/abs/2210.05040


Gravitational waves from merging binary black holes can be used to shed light on poorly understood aspects of massive binary stellar evolution, such as the evolution of massive stars (including their mass-loss rates), the common envelope phase, and the rate at which massive stars form throughout the cosmic history of the Universe. In this paper we explore the \emph{correlated} impact of these phases on predictions for the merger rate and chirp mass distribution of merging binary black holes, aiming to identify possible degeneracies between model parameters. In many of our models, a large fraction (more than 70% of detectable binary black holes) arise from the chemically homogeneous evolution scenario; these models tend to over-predict the binary black hole merger rate and produce systems which are on average too massive. Our preferred models favour enhanced mass-loss rates for helium rich Wolf–Rayet stars, in tension with recent theoretical and observational developments. We identify correlations between the impact of the mass-loss rates of Wolf–Rayet stars and the metallicity evolution of the Universe on the rates and properties of merging binary black holes. Based on the observed mass distribution, we argue that the $\sim 10\%$ of binary black holes with chirp masses greater than $40$ M$_\odot$ (the maximum predicted by our models) are unlikely to have formed through isolated binary evolution, implying a significant contribution (> 10%) from other formation channels such as dense star clusters or active galactic nuclei. Our models will enable inference on the uncertain parameters governing binary evolution in the near future.

Read this paper on arXiv…

S. Stevenson and T. Clarke
Wed, 12 Oct 22
70/75

Comments: 21 pages, 17 figures. Accepted for publication in MNRAS

Searching Lorentz invariance violation from cosmic photon attenuation [HEAP]

http://arxiv.org/abs/2210.05563


Lorentz invariance violation~(LIV) can change the threshold behavior predicted by special relativity and cause threshold anomalies which affect the propagation of cosmic photons. In this work, we focus on the threshold anomaly effect on cosmic photon attenuations by extragalactic background light~(EBL) and discuss how to identify LIV from observations of very high energy~(VHE) photons propagated from long distance in the universe. We point out that the Large High Altitude Air Shower Observatory~(LHAASO), one of the most sensitive gamma-ray detector arrays currently operating at TeV and PeV energies, is an ideal facility for performing such LIV searching.

Read this paper on arXiv…

H. Li and B. Ma
Wed, 12 Oct 22
71/75

Comments: 10 latex pages, 7 figures

Constraining ultralight vector dark matter with the Parkes Pulsar Timing Array second data release [CEA]

http://arxiv.org/abs/2210.03880


Composed of ultralight bosons, fuzzy dark matter provides an intriguing solution to challenges that the standard cold dark matter model encounters on sub-galactic scales. The ultralight dark matter with mass $m\sim10^{-23} \rm{eV}$ will induce a periodic oscillation in gravitational potentials with a frequency in the nanohertz band, leading to observable effects in the arrival times of radio pulses from pulsars. Unlike scalar dark matter, pulsar timing signals induced by the vector dark matter are dependent on the oscillation direction of the vector fields. In this work, we search for ultralight vector dark matter in the mass range of $[2\times 10^{-24}, 2\times 10^{-22}]{\rm{eV}}$ through its gravitational effect in the Parkes Pulsar Timing Array (PPTA) second data release. Since no statistically significant detection is made, we place $95\%$ upper limits on the local dark matter density as $\rho_{\rm{\tiny{VF}}} \lesssim 5{\rm{GeV/cm^{3}}}$ for $m\lesssim 10^{-23}{\rm{eV}}$. As no preferred direction is found for the vector dark matter, these constraints are comparable to those given by the scalar dark matter search with an earlier 12-year data set of PPTA.

Read this paper on arXiv…

Y. Wu, Z. Chen, Q. Huang, et. al.
Tue, 11 Oct 22
1/92

Comments: 9 pages, 3 figures, 2 tables; accepted for publication as a Letter in Phys. Rev. D

Nomen non est omen: why it is too soon to identify ultra-compact objects as black holes [CL]

http://arxiv.org/abs/2210.03750


Black holes play a pivotal role in the foundations of physics, but there is an alarming discrepancy between what is considered to be a black hole in observational astronomy and theoretical studies. Despite recent claims to the contrary, we argue that identifying the observed astrophysical black hole candidates as genuine black holes is not justified based on the currently available observational data, and elaborate on the necessary evidence required to support such a remarkable claim. In addition, we investigate whether the predictions of semiclassical gravity are equally compatible with competing theoretical models, and find that semiclassical arguments favor horizonless configurations.

Read this paper on arXiv…

S. Murk
Tue, 11 Oct 22
3/92

Comments: 4 pages, 1 figure. Comments welcome!

Galaxy formation catalyzed by leaky "black'' holes, and the JWST [CL]

http://arxiv.org/abs/2210.03742


We have proposed that galaxy formation is catalyzed by the collision of infalling and outstreaming particles from leaky, horizonless “black” holes. This gives an estimate of the local ($z \sim 0$) disk galaxy scale length as $ \ell \sim (\pi a_0^2 \rho_H)^{-1} \simeq 3.2\, {\rm kpc}$, where $a_0$ is the Bohr radius and $\rho_H$ is the density of atomic hydrogen in the proto-galactic region. This formula is in good agreement with observation, and suggests that the scale size of galaxies is fundamentally a property of atomic hydrogen. When scaled back to the early universe at redshift $z\simeq 11$, this formula predicts a very small disk galaxy scale length of $3200/(12^3) \sim 2\, pc$, which would correspond to galaxies seen as single pixels in the James Webb Space Telescope. With this prediction in mind, we suggest a possible method for estimating the diameter of sub-pixel sized galaxies by observing their transit between adjacent pixels.

Read this paper on arXiv…

S. Adler
Tue, 11 Oct 22
10/92

Comments: 3 pages

Probing Formation of Double Neutron Star Binaries around 1mHz with LISA [HEAP]

http://arxiv.org/abs/2210.04407


We propose a novel method to examine whether Galactic double neutron star binaries are formed in the LISA band. In our method, we assign an effective time fraction $\tau$ to each double neutron star binary detected by LISA. This fraction is given as a function of the observed orbital period and eccentricity and should be uniformly distributed in the absence of in-band binary formation. Applying statistical techniques such as the Kolmogorov-Smirnov test to the actual list of $\tau$, we can inspect the signature of the in-band binary formation. We discuss the prospects of this method, paying close attention to the available sample number of Galactic double neutron star binaries around 1mHz.

Read this paper on arXiv…

L. McNeill and N. Seto
Tue, 11 Oct 22
16/92

Comments: 9 pages, 3 figures

Deep learning method in testing the cosmic distance duality relation [CEA]

http://arxiv.org/abs/2210.04228


The cosmic distance duality relation (DDR) is constrained from the combination of type-Ia supernovae (SNe Ia) and strong gravitational lensing (SGL) systems using deep learning method. To make use of the full SGL data, we reconstruct the luminosity distance from SNe Ia up to the highest redshift of SGL using deep learning, then it is compared with the angular diameter distance obtained from SGL. Considering the influence of lens mass profile, we constrain the possible violation of DDR in three lens mass models. Results show that in the SIS model and EPL model, DDR is violated at high confidence level, with the violation parameter $\eta_0=-0.193^{+0.021}{-0.019}$ and $\eta_0=-0.247^{+0.014}{-0.013}$, respectively. In the PL model, however, DDR is verified within 1$\sigma$ confidence level, with the violation parameter $\eta_0=-0.014^{+0.053}_{-0.045}$. Our results demonstrate that the constraints on DDR strongly depend on the lens mass models. Given a specific lens mass model, DDR can be constrained at a precision of $\textit{O}(10^{-2})$ using deep learning.

Read this paper on arXiv…

L. Tang, H. Lin and L. Liu
Tue, 11 Oct 22
21/92

Comments: 11 pages,4 figures

Effect of Earth-Moon's gravity on TianQin's range acceleration noise. II. Impact of orbit selection [CL]

http://arxiv.org/abs/2210.03944


The paper is a sequel to our previous work (Zhang et al. Phys. Rev. D 103, 062001 (2021)). For proposed geocentric space-based gravitational wave detectors such as TianQin, gLISA, and GADFLI, the gravity-field disturbances, i.e., the so called “orbital noise”, from the Earth-Moon system on the sensitive intersatellite laser interferometric measurements should be carefully evaluated and taken into account in the concept studies. Based on TianQin, we investigate how the effect, in terms of frequency spectra, varies with different choices of orbital orientations and radii through single-variable studies, and present the corresponding roll-off frequencies that may set the lower bounds of the targeted detection bands. The results, including the special cases of geostationary orbits (gLISA/GADFLI) and repeat orbits, can provide a useful input to orbit and constellation design for future geocentric missions.

Read this paper on arXiv…

C. Luo and X. Zhang
Tue, 11 Oct 22
26/92

Comments: 8 pages, 9 figures

A convolutional neural network to distinguish glitches from minute-long gravitational wave transients [CL]

http://arxiv.org/abs/2210.04588


Gravitational wave bursts are transient signals distinct from compact binary mergers that arise from a wide variety of astrophysical phenomena. Because most of these phenomena are poorly modeled, the use of traditional search methods such as matched filtering is excluded. Bursts include short ($<$10 seconds) and long (from 10 to a few hundreds of seconds) duration signals for which the detection is constrained by environmental and instrumental transient noises called glitches. Glitches contaminate burst searches, reducing the amount of useful data and limiting the sensitivity of current algorithms. It is therefore of primordial importance to locate and distinguish them from potential burst signals. In this paper, we propose to train a convolutional neural network to detect glitches in the time-frequency space of the cross-correlated LIGO noise. We show that our network is retrieving more than 95$\%$ of the glitches while being trained only on a subset of the existing glitch classes highlighting the sensitivity of the network to completely new glitch classes.

Read this paper on arXiv…

V. Boudart
Tue, 11 Oct 22
37/92

Comments: 12 pages, 15 figures

Primordial black holes from stochastic tunnelling [CEA]

http://arxiv.org/abs/2210.03812


If the inflaton gets trapped in a local minimum of its potential shortly before the end of inflation, it escapes by building up quantum fluctuations in a process known as stochastic tunnelling. In this work we study cosmological fluctuations produced in such a scenario, and how likely they are to form Primordial Black Holes (PBHs). This is done by using the stochastic-$\delta N$ formalism, which allows us to reconstruct the highly non-Gaussian tails of the distribution function of the number of $e$-folds spent in the false-vacuum state. We explore two different toy models, both analytically and numerically, in order to identify which properties do or do not depend on the details of the false-vacuum profile. We find that when the potential barrier is small enough compared to its width, $\Delta V/V < \Delta\phi^2/M_{\text{Pl}}^2$, the potential can be approximated as being flat between its two local extrema, so results previously obtained in a “flat quantum well” apply. Otherwise, when $\Delta V/V < V/M_{\text{Pl}}^4$, the PBH abundance depends exponentially on the height of the potential barrier, and when $\Delta V/V > V/M_{\text{Pl}}^4$ it depends super-exponentially ( i.e. as the exponential of an exponential) on the barrier height. In that later case PBHs are massively produced. This allows us to quantify how much flat inflection points need to be fine-tuned. In a deep false vacuum, we also find that slow-roll violations are typically encountered unless the potential is close to linear. This motivates further investigations to generalise our approach to non-slow-roll setups.

Read this paper on arXiv…

C. Animali and V. Vennin
Tue, 11 Oct 22
49/92

Comments: 25 pages without appendix ( 36 pages in total ), 13 figures

Fully nonlinear Jeans instabilities for expanding Newtonian universes under homogeneous and isotropic perturbations [CL]

http://arxiv.org/abs/2210.04657


Based on mathematically rigorous analysis of nonlinear differential equations studied in our companion article [1], we construct a model which describes the \textit{nonlinear} gravitational instability on a local portion of the universe characterized by the expanding Newtonian universe. In this portion, the perturbations are homogeneous and isotropic. This result, to some extent, can be viewed as a nonlinear version of the Jeans instability. The growth rate of the relative density due to the nonlinear effects is much faster (at least $\sim \exp(t^{\frac{2}{3}})$ or blowup at a finite time according to the data) than the one predicted by the classical linear version of the Jeans instability ($\sim t^{\frac{2}{3}}$), and it leads to a better, or potentially substantial impacts on, understanding of the formation of the nonlinear structures in the universe and stellar systems. This article associated with [1] provides a new window into the rigorously mathematical and robust method, instead of the most used approximations and numerical calculations, of the fully nonlinear analysis of the Jeans instability for general cases.

Read this paper on arXiv…

C. Liu
Tue, 11 Oct 22
53/92

Comments: 15 pages

Accumulating errors in tests of general relativity with the Einstein Telescope: overlapping signals and inaccurate waveforms [CL]

http://arxiv.org/abs/2210.04769


Observations of gravitational waves (GWs) from compact binary coalescences provide powerful tests of general relativity (GR), but systematic errors in data analysis could lead to incorrect scientific conclusions. This issue is especially serious in the third-generation GW detectors in which the signal-to-noise ratio (SNR) is high and the number of events is large. In this work, we investigate the impacts of overlapping signals and inaccurate waveform models on tests of general relativity. We simulate mock catalogs for Einstein Telescope and perform parametric tests of GR using waveform models with different levels of inaccuracy. We find the systematic error could accumulate towards false deviations of GR when combining results from multiple events, even though data from most events prefers GR. The waveform inaccuracies contribute most to the systematic errors, but a high merger rate could magnify the effects of systematics due to the incorrect removal of detected overlapping signals. We also point out that testing GR using selected events with high SNR is even more vulnerable to false deviations from GR. The problem of error accumulation is universal; we emphasize that it should be taken into consideration in future catalog-level data analysis, and further investigations, particularly in waveform accuracy, will be essential for third generation detectors.

Read this paper on arXiv…

Q. Hu and J. Veitch
Tue, 11 Oct 22
58/92

Comments: 9 pages, 4 figures

The Possibility of Mirror Planet as Planet Nine in Solar System [EPA]

http://arxiv.org/abs/2210.04147


A series of dynamical anomalies in the orbits of distant trans-Neptunian objects points to a new celestial body (usually named Planet Nine) in the solar system. In this draft, we point out that a mirror planet captured from the outer solar system or formed in the solar system is also a possible candidate. The introduction of the mirror matter model is due to an unbroken parity symmetry and is a potential explanation for dark matter. This mirror planet has null or fainter electromagnetic counterparts with a smaller optical radius and might be explored through gravitational effects.

Read this paper on arXiv…

P. Wang, Y. Tang, L. Zu, et. al.
Tue, 11 Oct 22
65/92

Comments: N/A

The JWST High Redshift Observations and Primordial Non-Gaussianity [CEA]

http://arxiv.org/abs/2210.04812


Several bright and massive galaxy candidates at high redshifts have been recently observed by the James Webb Space Telescope. Such early massive galaxies seem difficult to reconcile with standard $\Lambda$ Cold Dark Matter model predictions. We discuss under which circumstances such observed massive galaxy candidates can be explained by introducing primordial non-Gaussianity in the initial conditions of the cosmological perturbations.

Read this paper on arXiv…

M. Biagetti, G. Franciolini and A. Riotto
Tue, 11 Oct 22
69/92

Comments: 10 pages, 4 figures

Experimental and observational tests of antigravity [CEA]

http://arxiv.org/abs/2210.03445


Whereas repulsive gravity was considered as a fringe concept until the mid-1990’s, the growingexperimental evidence since this epoch for repulsive gravity, in what is now called Dark Energy,for lack of a better understanding of its nature, has led to a vast literature in order to attemptto characterize this repulsive component, and notably its equation of state. In the following, Iwill show that we can use cosmology to test the hypothesis that antimatter is at the origin ofrepulsive gravity, may play the role of a Dark Energy component and, more surprisingly, maymimic the presence of Dark Matter, and justify the MOND phenomenology. More directly,three experiments, AEgIS, ALPHA-g and Gbar, are attempting to measure the action ofgravitation on cold atoms of antihydrogen at CERN in a near future. Finally, I note thatCP violation might be explained by antigravity and I briefly recall the motivations for thisassertion.

Read this paper on arXiv…

G. Chardin
Mon, 10 Oct 22
3/59

Comments: 33rd Rencontres de Blois: Exploring the Dark Universe, May 2022, Blois, France

A class of cosmological models with spatially constant sign-changing curvature [CL]

http://arxiv.org/abs/2209.11184


We construct globally hyperbolic spacetimes such that each slice ${t=t_0}$ of the universal time $t$ is a model space of constant curvature $k(t_0)$ which may not only vary with $t_0\in\mathbb{R}$ but also change its sign. The metric is smooth and slightly different to FLRW spacetimes, namely, $g=-dt^2+dr^2+ S_{k(t)}^2(r) g_{\mathbb{S}^{n-1}}$, where $g_{\mathbb{S}^{n-1}}$ is the metric of the standard sphere, $S_{k(t)}(r)=\sin(\sqrt{k(t)}\, r)/\sqrt{k(t)}$ when $k(t)\geq 0$ and $S_{k(t)}(r)=\sinh(\sqrt{-k(t)}\, r)/\sqrt{-k(t)}$ when $k(t)\leq 0$. In the open case, the $t$-slices are (non-compact) Cauchy hypersurfaces of curvature $k(t)\leq 0$, thus homeomorphic to $\mathbb{R}^n$; a typical example is $k(t)=-t^2$ (i.e., $S_{k(t)}(r)=\sinh(tr)/t$). In the closed case, $k(t)>0$ somewhere, a slight extension of the class shows how the topology of the $t$-slices changes. This makes at least one comoving observer to disappear in finite time $t$ showing some similarities with an inflationary expansion. Anyway, the spacetime is foliated by Cauchy hypersurfaces homeomorphic to spheres, not all of them $t$-slices.

Read this paper on arXiv…

M. Sánchez
Mon, 10 Oct 22
5/59

Comments: Minor modifications including the correction of an errata (Remark 4.7) and clarifications on the model (Remark 4.10) as well as on its possible links with inflation. 18 pages, 2 figures

Measuring properties of primordial black hole mergers at cosmological distances: effect of higher order modes in gravitational waves [CEA]

http://arxiv.org/abs/2210.03132


Primordial black holes (PBHs) may form from the collapse of matter overdensities shortly after the Big Bang. One may identify their existence by observing gravitational wave (GW) emissions from merging PBH binaries at high redshifts $z\gtrsim 30$, where astrophysical binary black holes (BBHs) are unlikely to merge. The next-generation ground-based GW detectors, Cosmic Explorer and Einstein Telescope, will be able to observe BBHs with total masses of $\mathcal{O}(10-100)~M_{\odot}$ at such redshifts. This paper serves as a companion paper of arXiv:2108.07276, focusing on the effect of higher-order modes (HoMs) in the waveform modeling, which may be detectable for these high redshift BBHs, on the estimation of source parameters. We perform Bayesian parameter estimation to obtain the measurement uncertainties with and without HoM modeling in the waveform for sources with different total masses, mass ratios, orbital inclinations and redshifts observed by a network of next-generation GW detectors. We show that including HoMs in the waveform model reduces the uncertainties of redshifts and masses by up to a factor of two, depending on the exact source parameters. We then discuss the implications for identifying PBHs with the improved single-event measurements, and expand the investigation of the model dependence of the relative abundance between the BBH mergers originating from the first stars and the primordial BBH mergers as shown in arXiv:2108.07276.

Read this paper on arXiv…

K. Ng, B. Goncharov, S. Chen, et. al.
Mon, 10 Oct 22
7/59

Comments: 11 pages, 11 figures

Constraining primordial black holes with relativistic degrees of freedom [CEA]

http://arxiv.org/abs/2210.03476


Scalar perturbations in the early Universe create over-dense regions that can collapse into primordial black holes (PBH). This process emits scalar-induced gravitational waves (SIGW) that behaves like an extra radiation component and contributes to the relativistic degrees of freedom ($N_{\rm{eff}}$). We show that $N_{\rm{eff}}$ limits from cosmic microwave background (CMB) give promising sensitivities on both the abundance of PBHs and the primordial curvature perturbation ($\mathcal{P}{\mathcal{R}}(k)$) at small scales. We show that {\it Planck} and ACTPol data can exclude supermassive PBHs with peak mass $M{\bullet} \in [3 \times 10^{5}, 5 \times 10^{10}] {\rm{M}}{\odot}$ as the major component of dark matter, depending on the shape of the PBHs mass distribution. Future CMB-S4 mission is capable of broadening this limit to a vast PBH mass window of $M{\bullet} \in [8 \times 10^{-5}, 5 \times 10^{10}] {\rm{M}}{\odot}$, covering sub-stellar masses. These limits correspond to the enhanced sensitivity of $\mathcal{P}{\mathcal{R}}(k)$ on scales of $k \in [10^1, 10^{22}]\ \rm{Mpc^{-1}}$, which is much smaller than those scales probed by direct perturbation power spectra (CMB and large-scale structure).

Read this paper on arXiv…

J. Cang, Y. Ma and Y. Gao
Mon, 10 Oct 22
19/59

Comments: 7 pages, 3 figures

Palatini formulation of the conformally invariant $f\left(R, L_m\right)$ gravity theory [CL]

http://arxiv.org/abs/2210.03631


We investigate the field equations of the conformally invariant models of gravity with curvature-matter coupling, constructed in Weyl geometry, by using the Palatini formalism. We consider the case in which the Lagrangian is given by the sum of the square of the Weyl scalar, of the strength of the field associated to the Weyl vector, and a conformally invariant geometry-matter coupling term, constructed from the matter Lagrangian and the Weyl scalar. After substituting the Weyl scalar in terms of its Riemannian counterpart, the quadratic action is defined in Riemann geometry, and involves a nonminimal coupling between the Ricci scalar and the matter Lagrangian. For the sake of generality, a more general Lagrangian, in which the Weyl vector is nonminmally coupled with an arbitrary function of the Ricci scalar, is also considered. By varying the action independently with respect to the metric and the connection, the independent connection can be expressed as the Levi-Civita connection of an auxiliary, Ricci scalar and Weyl vector dependent metric, which is related to the physical metric by means of a conformal transformation. The field equations are obtained in both the metric and the Palatini formulations. The cosmological implications of the Palatini field equations are investigated for three distinct models corresponding to different forms of the coupling functions. A comparison with the standard $\Lambda$CDM model is also performed, and we find that the Palatini type cosmological models can give an acceptable description of the observations.

Read this paper on arXiv…

T. Harko and S. Shahidi
Mon, 10 Oct 22
20/59

Comments: 17 pages, 6 figures, accepted for publication in EPJC

Towards a more robust algorithm for computing the Kerr quasinormal mode frequencies [CL]

http://arxiv.org/abs/2210.03657


Leaver’s method has been the standard for computing the quasinormal mode (QNM) frequencies for a Kerr black hole (BH) for a few decades. We start with a spectral variant of Leaver’s method introduced by Cook and Zalutskiy (arXiv: 1410.7698) and propose improvements in the form of computing the necessary derivatives analytically, rather than by numerical finite differencing. We also incorporate this derivative information into qnm, a Python package which finds the QNM frequencies via the spectral variant of Leaver’s method. We confine ourselves to first derivatives only.

Read this paper on arXiv…

S. Tanay
Mon, 10 Oct 22
36/59

Comments: 6 pages, 1 figure

Eccentricity to the rescue! Detecting Accelerating Eccentric Binaries in the LISA Band [HEAP]

http://arxiv.org/abs/2210.03129


Many gravitational wave (GW) sources in the LISA band are expected to have non-negligible eccentricity. Furthermore, many of them can undergo acceleration because they reside in the presence of a tertiary. Here we develop analytical and numerical methods to quantify how the compact binary’s eccentricity enhances the detection of its peculiar acceleration. We show that the general relativistic precession pattern can disentangle the binary’s acceleration-induced frequency shift from the chirp-mass-induced frequency shift in GW template fitting, thus relaxing the signal-to-noise ratio requirement for distinguishing the acceleration by a factor of $10\sim100$. Moreover, by adopting the GW templates of the accelerating eccentric compact binaries, we can enhance the acceleration measurement accuracy by a factor of $\sim100$, compared to the zero-eccentricity case, and detect the source’s acceleration even if it does not change during the observational time. For example, a stellar-mass binary black hole (BBH) with moderate eccentricity in the LISA band yields an error of the acceleration measurement $\sim10^{-7}m\cdot s^{-2}$ for $\rm{SNR}=20$ and observational time of $4$ yrs. In this example, we can measure the BBHs’ peculiar acceleration even when it is $\sim1\rm pc$ away from a $4\times 10^{6}\rm M_{\odot}$ SMBH. Our results highlight the importance of eccentricity to the LISA-band sources and show the necessity of developing GW templates for accelerating eccentric compact binaries.

Read this paper on arXiv…

Z. Xuan, S. Naoz and X. Chen
Mon, 10 Oct 22
37/59

Comments: 14 pages (+references), 9 figures. Submitted to PRD

Relativistic effects in a mildly recycled pulsar binary: PSR J1952+2630 [HEAP]

http://arxiv.org/abs/2210.03464


We report the results of timing observations of PSR J1952+2630, a 20.7 ms pulsar in orbit with a massive white dwarf companion. With the increased timing baseline, we obtain improved estimates for astrometric, spin, and binary parameters for this system. We get an improvement of an order of magnitude on the proper motion, and, for the first time, we detect three post-Keplerian parameters in this system: the advance of periastron, the orbital decay, and the Shapiro delay. We constrain the pulsar mass to 1.20$^{+0.28}{-0.29}\rm M{\odot}$ and the mass of its companion to 0.97$^{+0.16}{-0.13}\rm M{\odot}$. The current value of $\dot{P}{\rm b}$ is consistent with GR expectation for the masses obtained using $\dot{\omega}$ and $h_3$. The excess represents a limit on the emission of dipolar GWs from this system. This results in a limit on the difference in effective scalar couplings for the pulsar and companion (predicted by scalar-tensor theories of gravity; STTs) of $|\alpha{\rm p}-\alpha_{\rm c}| < 4.8 \times 10^{-3}$, which does not yield a competitive test for STTs. However, our simulations of future campaigns of this system show that by 2032, the precision of $\dot{P}{\rm b}$ and $\dot{\omega}$ will allow for much more precise masses and much tighter constraints on the orbital decay contribution from dipolar GWs, resulting in $|\alpha{\rm p}-\alpha_{\rm c}|<1.3 \times 10^{-3}$. We also present the constraints this system will place on the ${\alpha_0,\beta_0}$ parameters of DEF gravity by 2032. They are comparable to those of PSR J1738+0333. Unlike PSR J1738+0333, PSR J1952+2630 will not be limited in its mass measurement and has the potential to place even more restrictive limits on DEF gravity in the future. Further improvements to this test will likely be limited by uncertainties in the kinematic contributions to $\dot{P}_{\rm b}$ due to lack of precise distance measurements.

Read this paper on arXiv…

T. Gautam, P. Freire, A. Batrakov, et. al.
Mon, 10 Oct 22
38/59

Comments: 14 pages, 9 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics

Constraints on primordial curvature spectrum from primordial black holes and scalar-induced gravitational waves [CEA]

http://arxiv.org/abs/2210.03641


The observational data of primordial black holes and scalar-induced gravitational waves can constrain the primordial curvature perturbation at small scales. We parameterize the primordial curvature perturbation by a broken power law form and find that it is consistent with many inflation models that can produce primordial black holes, such as nonminimal derivative coupling inflation, scalar-tensor inflation, Gauss-Bonnet inflation, and K/G inflation. The constraints from primordial black holes on the primordial curvature power spectrum with the broken power law form are obtained, where the fraction of primordial black holes in dark matter is calculated by the peak theory. Both the real-space top-hat and the Gauss window functions are considered. The constraints on the amplitude of primordial curvature perturbation with Gauss window function are around three times larger than those with real-space top-hat window function. The constraints on the primordial curvature perturbation from the NANOGrav 12.5yrs data sets are displayed, where the NANOGrav signals are assumed as the scalar-induced gravitational waves, and only the first five frequency bins are used.

Read this paper on arXiv…

Z. Yi and Q. Fei
Mon, 10 Oct 22
41/59

Comments: 26 pages and 7 figures

Entropy and its conservation in expanding Universe [CL]

http://arxiv.org/abs/2210.03323


We investigate properties of the conserved charge in general relativity, recently proposed by one of the present authors with his collaborators, in the inflation era, the matter dominated era and the radiation dominated era of the expanding Universe. We show that the conserved charge becomes the Bekenstein-Hawking entropy in the inflation era, and it becomes the matter entropy and the radiation entropy in the matter and radiation dominated eras, respectively, while the charge itself is always conserved. These properties are qualitatively confirmed by a numerical analysis of a model with a scalar field and radiations. Results in this paper provide more evidences on the interpretation that the conserved charge in general relativity corresponds to entropy.

Read this paper on arXiv…

S. Aoki and K. Kawana
Mon, 10 Oct 22
47/59

Comments: 5 pages, 1 figure

The Instantaneous Redshift Difference of Gravitationally Lensed Images: Theory and Observational Prospects [CEA]

http://arxiv.org/abs/2210.03322


Due to the expansion of our Universe, the redshift of distant objects changes with time. Although the amplitude of this redshift drift is small, it will be measurable with a decade-long campaigns on the next generation of telescopes. Here we present an alternative view of the redshift drift which captures the expansion of the universe in single epoch observations of the multiple images of gravitationally lensed sources. Considering a sufficiently massive lens, with an associated time delay of order decades, simultaneous photons arriving at a detector would have been emitted decades earlier in one image compared to another, leading to an instantaneous redshift difference between the images. We also investigate the effect of peculiar velocities on the redshift difference in the observed images. Whilst still requiring the observational power of the next generation of telescopes and instruments, the advantage of such a single epoch detection over other redshift drift measurements is that it will be less susceptible to systematic effects that result from requiring instrument stability over decade-long campaigns.

Read this paper on arXiv…

C. Wang, K. Bolejko and G. Lewis
Mon, 10 Oct 22
52/59

Comments: 6 pages, 5 figures

Solar Diffraction of LIGO-Band Gravitational Waves [CEA]

http://arxiv.org/abs/2210.02649


We show that chirping gravitational waves in the LIGO frequency band $f=1 – 5000$ Hz can be gravitationally diffracted by the Sun, due to the coincidence of its Fresnel length $r_F \propto \sqrt{1\, {\rm AU}/f}$ and the solar radius $r_\odot$. This solar diffraction is detectable through its frequency-dependent amplification of the wave, albeit with low event rates. Furthermore, we find that solar diffraction allows probing the inner solar profile with the chirping evolution of frequencies. A similar phenomenon can also help discover non-relativistic wave dark matter, as studied in a sequel. This work not only presents an interesting opportunity with ongoing and future LIGO-band missions but also develops the diffractive lensing of long-wavelength waves in the universe.

Read this paper on arXiv…

S. Jung and S. Kim
Fri, 7 Oct 22
4/62

Comments: 20 pages, 10 figures

Parity violation in the scalar trispectrum: no-go theorems and yes-go examples [CL]

http://arxiv.org/abs/2210.02907


We derive a set of no-go theorems and yes-go examples for the parity-odd primordial trispectrum of curvature perturbations. We work at tree-level in the decoupling limit of the Effective Field Theory of Inflation and assume scale invariance and a Bunch-Davies vacuum. We show that the parity-odd scalar trispectrum vanishes in the presence of any number of scalar fields with arbitrary mass and any parity-odd scalar correlator vanishes in the presence of any number of spinning fields with massless de Sitter mode functions, in agreement with the findings of Liu, Tong, Wang and Xianyu [1]. The same is true for correlators with an odd number of conformally-coupled external fields. We derive these results using both the (boostless) cosmological bootstrap, in particular the Cosmological Optical Theorem, and explicit perturbative calculations. We then discuss a series of yes-go examples by relaxing the above assumptions one at the time. In particular, we provide explicit results for the parity-odd trispectrum for (i) violations of scale invariance in single-clock inflation, (ii) the modified dispersion relation of the ghost condensate (non-Bunch-Davies vacuum), and (iii) interactions with massive spinning fields. Our results establish the parity-odd trispectrum as an exceptionally sensitive probe of new physics beyond vanilla inflation.

Read this paper on arXiv…

G. Cabass, S. Jazayeri, E. Pajer, et. al.
Fri, 7 Oct 22
12/62

Comments: 38 pages, 5 figures

Parameter Distributions of Binary Black Hole Mergers Near Supermassive Black Holes as Seen by Advanced Gravitational Wave Detectors [HEAP]

http://arxiv.org/abs/2210.02975


The environment surrounding supermassive black holes (SMBHs) in galactic nuclei (GNs) is expected to harbour stellar-mass binary black hole (BBH) populations. These binaries were suggested to form a hierarchical triple system with the SMBH, and gravitational perturbations from the SMBH can enhance the mergers of BBHs through Lidov-Kozai (LK) oscillations. Previous studies determined the expected binary parameter distribution for this merger channel in single GNs. Here we account for the different spatial distribution and mass distribution models of BBHs around SMBHs and perform direct high-precision regularized N-body simulations, including Post-Newtonian (PN) terms up to order PN2.5, to model merging BBH populations in single GNs. We use a full inspiral-merger-ringdown waveform model of BBHs with nonzero eccentricities and take into account the observational selection effect to determine the parameter distributions of LK-induced BBHs detected with single advanced GW detectors from all GNs in the Universe. We find that the detected mergers’ total binary mass distribution is tilted towards lower masses, and the mass ratio distribution is roughly uniform. The redshift distribution peaks between ~0.15-0.55, and the vast majority of binaries merge within redshift ~1.1. The fraction of binaries entering the LIGO/Virgo/KAGRA band with residual eccentricities >0.1 ranges between ~3-12%. We identify a negative correlation between residual eccentricity and mass parameters and a negative correlation between residual eccentricity and source distance. Our results for the parameter distributions and correlations among binary parameters may make it possible to disentangle this merger channel from other BBH merger channels statistically.

Read this paper on arXiv…

L. Gondán
Fri, 7 Oct 22
14/62

Comments: 15 pages, 2 figures, 3 tables, submitted to MNRAS

Testing gravity with gravitational waves $\times$ electromagnetic probes cross-correlations [CEA]

http://arxiv.org/abs/2210.02460


In a General Relativistic framework, Gravitational Waves (GW) and Electromagnetic (EM) waves are expected to respond in the same way to the effects of matter perturbations between the emitter and the observer. A different behaviour might be a signature of alternative theories of gravity. In this work we study the cross-correlation of resolved GW events (from compact objects mergers detected by the Einstein Telescope, either assuming or excluding the detection of an EM counterpart) and EM signals (coming both from the Intensity Mapping of the neutral hydrogen distribution and resolved galaxies from the SKA Observatory), considering weak lensing, angular clustering and their cross term ($\mathrm{L \times C}$) as observable probes. Cross-correlations of these effects are expected to provide promising information on the behaviour of these two observables, hopefully shedding light on beyond GR signatures. We perform a Fisher matrix analysis with the aim of constraining the ${\mu_0,\eta_0,\Sigma_0}$ parameters, either opening or keeping fixed the background parameters ${w_0,w_a}$. We find that, although lensing-only forecasts provide significantly unconstrained results, the combination with angular clustering and the cross-correlation of all three considered tracers (GW, IM, resolved galaxies) leads to interesting and competitive constraints. This offers a novel and alternative path to both multi-tracing opportunities for Cosmology and the Modified Gravity sector.

Read this paper on arXiv…

G. Scelfo, M. Berti, A. Silvestri, et. al.
Fri, 7 Oct 22
36/62

Comments: 33 pages, 10 figures, 4 tables

Effects of a Pre-inflationary de Sitter Bounce on the Primordial Gravitational Waves in $f(R)$ Gravity Theories [CL]

http://arxiv.org/abs/2210.02861


In this work we examine the effects of a pre-inflationary de Sitter bounce on the energy spectrum of the primordial gravitational waves. Specifically we assume that the Universe is described by several evolution patches, starting with a de Sitter pre-inflationary bounce which is followed by an quasi-de Sitter slow-roll inflationary era, followed by a constant equation of state parameter abnormal reheating era, which is followed by the radiation and matter domination eras and the late-time acceleration eras. The bounce and the inflationary era can be realized by vacuum $f(R)$ gravity and the abnormal reheating and the late-time acceleration eras by the synergy of $f(R)$ gravity and the prefect matter fluids present. Using well-known reconstruction techniques we find which $f(R)$ gravity can realize each evolution patch, except from the matter and radiation domination eras which are realized by the corresponding matter fluids. Accordingly, we calculate the damping factor of the primordial de Sitter bounce, and as we show, the signal can be detected by only one gravitational wave future experiment, in contrast to the case in which the bounce is absent. We discuss in detail the consequences of our results and the future perspectives.

Read this paper on arXiv…

V. Oikonomou
Fri, 7 Oct 22
43/62

Comments: Nuclear Physics B in press. arXiv admin note: text overlap with arXiv:2209.09781

Conservative Evolution of Black Hole Perturbations with Time-Symmetric Numerical Methods [CL]

http://arxiv.org/abs/2210.02550


The scheduled launch of the LISA Mission in the next decade has called attention to the gravitational self-force problem. Despite an extensive body of theoretical work, long-time numerical computations of gravitational waves from extreme-mass-ratio-inspirals remain challenging. This work proposes a class of numerical evolution schemes suitable to this problem based on Hermite integration. Their most important feature is time-reversal symmetry and unconditional stability, which enables these methods to preserve symplectic structure, energy, momentum and other Noether charges over long time periods. We apply Noether’s theorem to the master fields of black hole perturbation theory on a hyperboloidal slice of Schwarzschild spacetime to show that there exist constants of evolution that numerical simulations must preserve. We demonstrate that time-symmetric integration schemes based on a 2-point Taylor expansion (such as Hermite integration) numerically conserve these quantities, unlike schemes based on a 1-point Taylor expansion (such as Runge-Kutta). This makes time-symmetric schemes ideal for long-time EMRI simulations.

Read this paper on arXiv…

M. O’Boyle, C. Markakis, L. Silva, et. al.
Fri, 7 Oct 22
50/62

Comments: 43 pages, 8 figures

A unified model of inflation and dark energy based on the holographic spacetime foam [CL]

http://arxiv.org/abs/2210.02556


I present a model of inflation and dark energy in which the inflaton potential is constructed by imposing that a scalar field representing the classical energy of the spacetime foam inside the Hubble horizon is an exact solution to the cosmological equations. The resulting potential has the right properties to describe both the early and late expansion epochs of the universe in a unified picture.

Read this paper on arXiv…

D. Jiménez-Aguilar
Fri, 7 Oct 22
51/62

Comments: 6 pages, 4 figures

Jet Gravitational Waves [HEAP]

http://arxiv.org/abs/2210.02740


The acceleration of a jet to relativistic velocities produces a unique memory type gravitational waves (GW) signal: {\it Jet-GW}. I discuss here resent result concerning properties of these GWs and consider their detectability in current and proposed detectors. Classical sources are long and short Gamma-ray bursts as well as hidden jets in core-collapse supernovae. Detection of jet-GWs from these sources will require detectors, such as the proposed BBO, DECIGO and lunar based detectors, that will operate in the deciHz band. The current LVK detectors could detect jet-GWs from a Galactic SGR flare if it is sufficiently asymmetric. Once detected these signals could reveal information concerning jet acceleration and collimation that cannot be explored otherwise.

Read this paper on arXiv…

T. Piran
Fri, 7 Oct 22
53/62

Comments: Published in “Looking Beyond the Frontiers of Science” Dedicated to the 80th Birthday of KK Phua, Edited By: L Brink , N-P Chang , D H Feng, K Fujikawa, M-L Ge, L C Kwek, C H Oh and S R Wadia, World Scientific Publications, July 2022. arXiv admin note: text overlap with arXiv:2107.12418

Quantum Oppenheimer-Snyder and Swiss Cheese models [CL]

http://arxiv.org/abs/2210.02253


By considering the quantum Oppenheimer-Snyder model in loop quantum cosmology, a new quantum black hole model whose metric tensor is a suitably deformed Schwarzschild one is derived. The quantum effects imply a lower bound on the mass of the black hole produced by the collapsing dust ball. For the case of larger masses where the event horizon does form, the maximal extension of the spacetime and its properties are investigated. By discussing the opposite scenario to the quantum Oppenheimer-Snyder, a quantum Swiss Cheese model is obtained with a bubble surrounded by the quantum universe. This model is analogous to the black hole cosmology or fecund universes where the big bang is related to a white hole. Thus our models open a new window to the cosmological phenomenology.

Read this paper on arXiv…

J. Lewandowski, Y. Ma, J. Yang, et. al.
Thu, 6 Oct 22
7/77

Comments: 5+2 pages, 3 figures

Determining parameters of a spherical black hole with thin accretion disk by observing its shadow [CL]

http://arxiv.org/abs/2210.02164


We revisit the classic system of a spherically symmetric black hole in general relativity (i.e., a Schwarzschild black hole) surrounded by a geometrically thin accretion disk. Our purpose is to examine whether one can determine three parameters of this system (i.e., black hole mass $M$; distance between the black hole and an observer $r_o$; inclination angle $i$) solely by observing the accretion disk and the black-hole shadow. A point in our analysis is to allow $r_o$ to be finite, which is set to be infinite in most relevant studies. First, it is shown that one can determine the values of $(r_o/M, i)$, where $M/r_o$ is the so-called angular gravitational radius, from the size and shape of shadow. Then, it is shown that if one additionally knows the accretion rate $\dot{M}$ (resp.\ mass $M$) by any independent theoretical or observational approach, one can determine the values of $(M, r_o, i)$ [resp.\ $(\dot{M}, r_o, i)$] without degeneracy, in principle, from the value of flux at any point on the accretion disk.

Read this paper on arXiv…

K. Hioki and U. Miyamoto
Thu, 6 Oct 22
13/77

Comments: 25 pages, 11 figures

The Missing Link Between Black Holes in High-Mass X-ray Binaries and Gravitational-Wave Sources: Observational Selection Effects [HEAP]

http://arxiv.org/abs/2210.01825


There are few observed high-mass X-ray binaries (HMXBs) that harbor massive black holes, and none are likely to result in a binary black hole (BBH) that merges within a Hubble time; however, we know that massive merging BBHs exist from gravitational-wave observations. We investigate the role that X-ray and gravitational-wave observational selection effects play in determining the properties of their respective detected binary populations. We confirm that, as a result of selection effects, observable HMXBs and observable BBHs form at different redshifts and metallicities, with observable HMXBs forming at much lower redshifts and higher metallicities than observable BBHs. We also find disparities in the mass distributions of these populations, with observable merging BBH progenitors pulling to higher component masses relative to the full observable HMXB population. Fewer than $3\%$ of observable HMXBs host black holes $> 35M_{\odot}$ in our simulated populations. Furthermore, we find the probability that a detectable HMXB will merge as a BBH system within a Hubble time is $\simeq 0.6\%$. Thus, it is unsurprising that no currently observed HMXB is predicted to form a merging BBH with high probability.

Read this paper on arXiv…

C. Liotine, M. Zevin, C. Berry, et. al.
Thu, 6 Oct 22
22/77

Comments: 16 pages, 6 figures, 1 table

Dynamics of dwarf galaxies in $f(R)$ gravity [GA]

http://arxiv.org/abs/2210.02306


We use the kinematic data of the stars in eight dwarf spheroidal galaxies to assess whether $f(R)$ gravity can fit the observed profiles of the line-of-sight velocity dispersion of these systems without resorting to dark matter. Our model assumes that each galaxy is spherically symmetric and has a constant velocity anisotropy parameter $\beta$ and constant mass-to-light ratio consistent with stellar population synthesis models. We solve the spherical Jeans equation that includes the Yukawa-like gravitational potential appearing in the weak field limit of $f(R)$ gravity, and a Plummer density profile for the stellar distribution. The $f(R)$ velocity dispersion profiles depend on two parameters: the scale length $\xi^{-1}$, below which the Yukawa term is negligible, and the boost of the gravitational field $\delta>-1$. $\delta$ and $\xi$ are not universal parameters, but their variation within the same class of objects is expected to be limited. The $f(R)$ velocity dispersion profiles fit the data with a value $\xi^{-1}= 1.2^{+18.6}_{-0.9}$ Mpc for the entire galaxy sample. On the contrary, the values of $\delta$ show a bimodal distribution that picks at $\bar{\delta}=-0.986\pm0.002$ and $\bar{\delta}=-0.92\pm0.01$. These two values disagree at $6\sigma$ and suggest a severe tension for $f(R)$ gravity. It remains to be seen whether an improved model of the dwarf galaxies or additional constraints provided by the proper motions of stars measured by future astrometric space missions can return consistent $\delta$’s for the entire sample and remove this tension.

Read this paper on arXiv…

I. Martino, A. Diaferio and L. Ostorero
Thu, 6 Oct 22
24/77

Comments: 11 pages, 4 figures, 2 Tables

Scalar overproduction in standard cosmology and predictivity of non-thermal dark matter [CL]

http://arxiv.org/abs/2210.02293


Stable scalars can be copiously produced in the Early Universe even if they have no coupling to other fields. We study production of such scalars during and after (high scale) inflation, and obtain strong constraints on their mass scale. Quantum gravity-induced Planck-suppressed operators make an important impact on the abundance of dark relics. Unless the corresponding Wilson coefficients are very small, they normally lead to overproduction of dark states. In the absence of a quantum gravity theory, such effects are uncontrollable, bringing into question predictivity of many non-thermal dark matter models. These considerations may have non-trivial implications for string theory constructions, where scalar fields are abundant.

Read this paper on arXiv…

O. Lebedev
Thu, 6 Oct 22
27/77

Comments: 22 pages

Weak lensing of gravitational waves in wave optics: Beyond the Born approximation [CEA]

http://arxiv.org/abs/2210.02062


Universe’s matter inhomogeneity gravitationally affects the propagation of gravitational waves (GWs), causing the lensing effect. Particularly, the weak lensing of GWs contains abundance of information about the small scale matter power spectrum and it has been studied within the range of the Born approximation. In this work, we investigate the validity of the Born approximation by accounting for the higher order terms in the gravitational potential $\Phi$. We first develop the formulation of the post-Born approximation, which is made by introducing a new variable. We then derive the expression of the magnitude and the phase of the amplification factor up to third order in $\Phi$ and compute the average and variance beyond the Born approximation. Our results suggest that the post-Born effect is indeed a few orders of magnitude smaller than the leading order contribution within almost all frequency ranges considered in this work except for the high frequency area $f\sim1000$ Hz, where the shot noise is dominant. Intriguingly, the number of necessary GW events for detecting the average, which originates purely from the post-Born effect, could become comparable or even smaller than the number required for detecting the variance, which appears at the level of the Born approximation. This indicates that the average is measurable with the same detection cost as the variance, even though it is only a few percent of the variance. On the other hand, we find that, even though the detection of the post-Born corrections to the variance would be possible in the case of the magnification, extracting the useful information to infer the shape of the matter power spectrum is still challenging even for the future generation GW detectors. This is due to the smallness of the post-Born effect and the difficulty of separating it from both the noise signal and the Born approximation effect.

Read this paper on arXiv…

M. Mizuno and T. Suyama
Thu, 6 Oct 22
31/77

Comments: 39 pages, 8 figures

Black hole thermodynamics from logotropic fluids [CL]

http://arxiv.org/abs/2210.02431


We show that Einstein’s field equations with a negative cosmological constant can admit black hole solutions whose thermodynamics coincides with that of logotropic fluids, recently investigated to heal some cosmological and astrophysical issues. For this purpose, we adopt the Anton-Schmidt equation of state, which represents a generalized version of logotropic fluids. We thus propose a general treatment to obtain an asymptotic anti-de Sitter metric, reproducing the thermodynamic properties of both Anton-Schmidt and logotropic fluids. Hence, we explore how to construct suitable spacetime functions, invoking an event horizon and fulfilling the null, weak, strong and dominant energy conditions. We further relax the strong energy condition to search for possible additional solutions. Finally, we discuss the optical properties related to a specific class of metrics and show how to construct an effective refractive index depending on the spacetime functions and the thermodynamic quantities of the fluid under study. We also explore possible departures with respect to the case without the fluid.

Read this paper on arXiv…

S. Capozziello, R. D’Agostino, A. Lapponi, et. al.
Thu, 6 Oct 22
32/77

Comments: 24 pages, 3 figures

Decay of superluminal neutrinos in the collinear approximation [CL]

http://arxiv.org/abs/2210.02222


The kinematics of the three body decay, with a modified energy-momentum relation of the particles due to a violation of Lorentz invariance, is presented in detail in the collinear approximation. The results are applied to the decay of superluminal neutrinos producing an electron-positron or a neutrino-antineutrino pair. Explicit expressions for the energy distributions, required for a study of the cascade of neutrinos produced in the propagation of superluminal neutrinos, are derived.

Read this paper on arXiv…

J. Carmona, J. Cortés, J. Relancio, et. al.
Thu, 6 Oct 22
37/77

Comments: 13 pages, 3 figures

Gravitational microlensing by dressed primordial black holes [CEA]

http://arxiv.org/abs/2210.02078


The accretion of dark matter around the primordial black holes (PBHs) could lead to the formation of surrounding minihalos, whose mass can be several orders of magnitude higher than the central PBH mass. The gravitational microlensing produced by such dressed PBHs could be quite different from that of the bare PBHs, which may greatly affect the constraints on the PBH abundance. In this paper, we study the gravitational microlensing produced by dressed PBHs in details. We find that all the microlensing effects by dressed PBHs have asymptotic behavior depending on the minihalo size, which can be used to predict the microlensing effects by comparing the halo size with the Einstein radius. When the minihalo radius and the Einstein radius are comparable, the effect of the density distribution of halo is significant to the microlensing. Applying the microlensing by dressed PBHs to the data of Optical Gravitational Lensing Experiment and Subaru/HSC Andromeda observations, we obtain the improved constraints on the PBH abundance. It shows that the existence of dark matter minihalos surrounding PBHs can strengthen the constraints on PBH abundance by several orders and can shift the constraints to the well-known mass window where PBHs can constitute all the dark matter.

Read this paper on arXiv…

R. Cai, T. Chen, S. Wang, et. al.
Thu, 6 Oct 22
46/77

Comments: 19 pages, 11 figures

Tabletop potentials for inflation from $f(R)$ gravity [CL]

http://arxiv.org/abs/2210.01828


We show that a large class of modified gravity theories (MOG) with the Jordan-frame Lagrangian $f(R)$ translate into scalar-field (scalaron) models with hilltop potentials in the Einstein frame. (A rare exception to this rule is provided by the Starobinsky model for which the corresponding scalaron potential is plateau-like for $\phi > 0$.) We find that MOG models featuring two distinct mass scales lead to scalaron potentials that have a flattened hilltop, or tabletop. Inflationary evolution in tabletop models agrees very well with CMB observations. Tabletop potentials therefore provide a new and compelling class of MOG-based inflationary models. By contrast, MOG models with a single mass scale generally correspond to steep hilltop potentials and fail to reproduce the CMB power spectrum. Inflationary evolution in hilltop/tabletop models can proceed in two alternative directions: towards the stable point at small $R$ describing the observable universe, or towards the asymptotic region at large $R$. The MOG models which we examine have several new properties including the fact that gravity can become asymptotically free, with $G_{\rm eff} \to 0$, at infinite or large finite values of the scalar curvature $R$. Interestingly a universe evolving towards the asymptotically free gravity region at large $R$ will either run into a ‘Big-Rip’ singularity, or inflate eternally.

Read this paper on arXiv…

Y. Shtanov, V. Sahni and S. Mishra
Thu, 6 Oct 22
60/77

Comments: 32 pages, 11 figures

Detectability of strongly lensed gravitational waves using model-independent image parameters [CL]

http://arxiv.org/abs/2210.01873


Strong gravitational lensing of gravitational waves (GWs) occurs when the GWs from a compact binary system travel near a massive object. The mismatch between a lensed signal and unlensed templates determines whether lensing can be identified in a particular GW event. For axisymmetric lens models, the lensed signal is traditionally calculated in terms of model-dependent lens parameters such as the lens mass $M_L$ and source position $y$. We propose that it is useful to parameterize this signal instead in terms of model-independent image parameters: the flux ratio $I$ and time delay $\Delta t_d$ between images. The functional dependence of the lensed signal on these image parameters is far simpler, facilitating data analysis for events with modest signal-to-noise ratios. In the geometrical-optics approximation, constraints on $I$ and $\Delta t_d$ can be inverted to constrain $M_L$ and $y$ for any lens model including the point mass (PM) and singular isothermal sphere (SIS) that we consider. We use our model-independent image parameters to determine the detectability of gravitational lensing in GW signals and find that for GW events with signal-to-noise ratios $\rho$ and total mass $M$, lensing should in principle be identifiable for flux ratios $I \gtrsim 2\rho^{-2}$ and time delays $\Delta t_d \gtrsim M^{-1}$.

Read this paper on arXiv…

S. Ali, E. Stoikos, E. Meade, et. al.
Thu, 6 Oct 22
62/77

Comments: 11 pages, 8 figures, submitted to PRD

Probing the Delay Time of Supermassive Black Hole Binary Mergers With Gravitational Waves [CL]

http://arxiv.org/abs/2209.14509


Merging supermassive black hole binaries is expected as a possible consequence of galaxy mergers, yet the detailed evolution path and underlying mechanisms of these binaries are still subject to large theoretical uncertainties. In this work, we propose to combine the (future) gravitational wave measurements of supermassive black hole binary merger events with the galaxy merger rate distributions from large-scale surveys/cosmological simulations, to infer the delay time of binary mergers, as a function of binary mass. The delay time encodes key information about binary evolution, which can be used to test the predictions of various evolution models. With a mock data set of supermassive black hole binary merger events, we discuss how to infer the distribution of delay time with hierarchical Bayesian inference and test evolution models with the Bayesian model selection method.

Read this paper on arXiv…

Y. Fang and H. Yang
Thu, 6 Oct 22
71/77

Comments: 14 pages, 10 figures

Closed-form solutions of spinning, eccentric binary black holes at 1.5 post-Newtonian order [CL]

http://arxiv.org/abs/2210.01605


The closed-form solution of the 1.5 post-Newtonian (PN) accurate binary black hole (BBH) Hamiltonian system has proven to be difficult to obtain for a long time since its introduction in 1966. Closed-form solutions of the PN BBH systems with arbitrary parameters (masses, spins, eccentricity) are required for modeling the gravitational waves (GWs) emitted by them. Accurate models of GWs are crucial for their detection by LIGO/Virgo and LISA. Only recently, two solution methods for solving the BBH dynamics were proposed in arXiv:1908.02927 (without using action-angle variables), and arXiv:2012.06586, arXiv:2110.15351 (action-angle based). This paper combines the ideas laid out in the above articles, fills the missing gaps and provides the two solutions which are fully 1.5PN accurate. We also present a public Mathematica package BBHpnToolkit which implements these two solutions and compares them with a fully numerical treatment. The level of agreement between these solutions provides a numerical verification for all the five actions constructed in arXiv:2012.06586, and arXiv:2110.15351. This paper hence serves as a stepping stone for pushing the action-angle-based solution to 2PN order via canonical perturbation theory.

Read this paper on arXiv…

R. Samanta, S. Tanay and L. Stein
Wed, 5 Oct 22
42/73

Comments: 13 pages, 3 figures

Gravitational waves from extreme-mass-ratio systems in astrophysical environments [CL]

http://arxiv.org/abs/2210.01133


We establish a generic, fully-relativistic formalism to study gravitational-wave emission by extreme-mass-ratio systems in spherically-symmetric, non-vacuum black-hole spacetimes. The potential applications to astrophysical setups range from black holes accreting baryonic matter to those within axionic clouds and dark matter environments, allowing to assess the impact of the galactic potential, of accretion, gravitational drag and halo feedback on the generation and propagation of gravitational-waves. We apply our methods to a black hole within a halo of matter. We find fluid modes imparted to the gravitational-wave signal (a clear evidence of the black hole fundamental mode instability) and the tantalizing possibility to infer galactic properties from gravitational-wave measurements by sensitive, low-frequency detectors.

Read this paper on arXiv…

V. Cardoso, K. Destounis, F. Duque, et. al.
Wed, 5 Oct 22
62/73

Comments: 7 pages, 3 figures, comments are welcome

On the possible implications of Dark Matter in the rings of Saturn: a conjecture [CL]

http://arxiv.org/abs/2210.01446


In this article we discuss some consequences of the well-known proposition of Fritz Zwicky [1], published in the nineteen thirties, that Dark Matter `mimics’ the inertia-gravitational behaviour of usual matter. In particular, we consider some special dynamical regions such as those of the Ring Systems of the gaseous giants at the edge of the Planetary System. This article is a continuation of an earlier paper [2], where it was shown that gravitationally interacting particles may remain near the Lagrange Points L4 and L5 for many thousands of years. This provides enough time for the Dark Matter, if present there, to interact with the usual matter. We discuss also a number of questions related to places which might be considered singular in the mathematical sense.

Read this paper on arXiv…

A. Ciulli and S. Ciulli
Wed, 5 Oct 22
68/73

Comments: 14 pages, 9 figures

Dynamical consistency conditions for rapid turn inflation [CL]

http://arxiv.org/abs/2210.00031


We derive consistency conditions for sustained slow roll and rapid turn inflation in two-field cosmological models with oriented scalar field space, which imply that inflationary models with field-space trajectories of this type are non-generic. In particular, we show that third order adiabatic slow roll, together with large and slowly varying turn rate, requires the scalar potential of the model to satisfy a certain nonlinear second order PDE, whose coefficients depend on the scalar field metric. We also derive consistency conditions for circular rapid turn trajectories with slow roll in two-field models with rotationally invariant field space metric as well as consistency conditions for slow roll inflationary solutions in the so called “rapid turn attractor” approximation. Finally, we argue that the rapid turn regime tends to have a natural exit after a limited number of e-folds.

Read this paper on arXiv…

L. Anguelova and C. Lazaroiu
Tue, 4 Oct 22
32/71

Comments: 32 pages

Issues in Palatini ${\cal{R}}^2$ inflation: Bounds on the Reheating Temperature [CL]

http://arxiv.org/abs/2210.00837


We consider ${\cal{R}}^2$-inflation in Palatini gravity, in the presence of scalar fields coupled to gravity. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$ – inflation models. We apply this formalism for the study of single-field inflationary models, whose potentials are monomials, $ V \sim h^{n} $, with $ n $ a positive even integer. We also study the Higgs model non-minimally coupled to gravity. With ${\cal{R}}^2$-terms coupled to gravity as $\sim \alpha {\cal{R}}^2 $, with $\alpha$ constant, the instantaneous reheating temperature $T_{ins}$, is bounded by $ T_{ins} \leq { 0.290 \, m_{Planck}} / {\, \alpha^{1/4}} $, with the upper bound being saturated for large $\alpha$. For such large $\alpha$ need go beyond slow-roll to calculate reliably the cosmological parameters, among these the end of inflation through which $T_{ins}$ is determined. In fact, as inflaton rolls towards the end of inflation point, the quartic in the velocity terms, unavoidable in Palatini gravity, play a significant role and can not be ignored. The values of $\alpha$, and other parameters, are constrained by cosmological data, setting bounds on the inflationary scale $M_{s} \sim 1/\sqrt{\alpha}$ and the reheating temperature of the Universe.

Read this paper on arXiv…

A. Lahanas
Tue, 4 Oct 22
46/71

Comments: 33 pages, 18 figures, PDFLaTeX

Effective Field Theory of Large Scale Structure in modified gravity and application to Degenerate Higher-Order Scalar-Tensor theories [CL]

http://arxiv.org/abs/2210.00772


In modified gravity, the one-loop matter power spectrum exhibits an ultraviolet divergence as shown in the framework of the degenerate higher-order scalar-tensor theory. To address this problem, we extend the effective field theory of large scale structure to modified gravity theories. We find that new counterterms appear and renormalize the ultraviolet divergence as a natural consequence of non-linearity in the modified Poisson equation. The renormalized one-loop matter power spectrum is useful to test modified gravity theories by comparing to observations.

Read this paper on arXiv…

S. Hirano and T. Fujita
Tue, 4 Oct 22
47/71

Comments: 10 pages, no figure

3D Photon Conserving Code for Time-dependent General Relativistic Radiative Transfer : CARTOON [HEAP]

http://arxiv.org/abs/2210.00686


We develop the 3-dimensional general relativistic radiative transfer code: CARTOON (Calculation code of Authentic Radiative Transfer based On phOton Number conservation in curved space-time) which is improved from the 2-dimensional code: ARTIST developed by Takahashi & Umemura (2017). In CARTOON, the frequency-integrated general relativistic radiative transfer equation is solved in a photon number-conserving manner, and the isotropic and coherent scattering in the zero angular momentum observers (ZAMO) frame and the fluid rest frame is incorporated. By calculating the average energy of photons, energy conservation of the radiation is also guaranteed. With the test calculations in 2-dimensional and 3-dimensional space, we have demonstrated that the wavefront propagation in black hole space-time can be correctly solved in CARTOON conserving photon numbers. The position of the wavefront coincides with the analytical solution and the number of photons remains constant until the wavefront reaches the event horizon. We also solve the radiative transfer equation on the geodesic reaching the observer’s screen. The time variation of the intensity map on the observer’s screen can be simultaneously and consistently calculated with the time variation of the radiation field around the black hole. In addition, the black hole shadow can be reproduced in moderately optically thin situations.

Read this paper on arXiv…

M. Takahashi, K. Ohsuga, R. Takahashi, et. al.
Tue, 4 Oct 22
52/71

Comments: 12 pages, 12 figures. Accepted for publication in MNRAS

Stochastic gravitational wave background: methods and Implications [CL]

http://arxiv.org/abs/2210.00761


Beyond individually resolvable gravitational wave events such as binary black hole and binary neutron star mergers, the superposition of many more weak signals coming from a multitude of sources is expected to contribute to an overall background, the so-called stochastic gravitational wave background. In this review, we give an overview of possible detection methods in the search for this background and provide a detailed review of the data-analysis techniques, focusing primarily on current Earth-based interferometric gravitational-wave detectors. In addition, various validation techniques aimed at reinforcing the claim of a detection of such a background are discussed as well. We conclude this review by listing some of the astrophysical and cosmological implications resulting from current upper limits on the stochastic background of gravitational waves.

Read this paper on arXiv…

N. Remortel, K. Janssens and K. Turbang
Tue, 4 Oct 22
55/71

Comments: 71 pages, 17 figures, review article

Black hole in quantum wave dark matter [CL]

http://arxiv.org/abs/2210.00523


In this work, we explored the effect of the fuzzy dark matter (FDM) (or wave dark matter) halo on a supermassive black hole (SMBH). Such a dark matter introduces a soliton core density profile, and we treat it ideally as a spherical distribution that surrounds the SMBH located at its center. In this direction, we obtained a new metric due to the union of the black hole and dark matter spacetime geometries. We applied the solution to the two known SMBH – Sgr. A* and M87* and used the empirical data for the shadow diameter by EHT to constrain the soliton core radius $r_\text{c}$ given some values of the boson mass $m_\text{b}$. Then, we examine the behavior of the shadow radius based on such constraints and relative to a static observer. We found that different shadow sizes are perceived at regions $r_\text{obs}<r_\text{c}$ and $r_\text{obs}>r_\text{c}$, and the deviation is greater for values $m_\text{b}<10^{-22}$ eV. Concerning the shadow behavior, we have also analyzed the effect of the soliton profile on the thin-accretion disk. Soliton dark matter effects manifest through the varying luminosity near the event horizon. We also analyzed the weak deflection angle and the produced Einstein rings due to soliton effects. We found considerable deviation, better than the shadow size deviation, for the light source near the SMBH with impact parameters comparable to the soliton core. Our results suggest the possible experimental detection of soliton dark matter effects using an SMBH at the galactic centers.

Read this paper on arXiv…

R. Pantig and A. Övgün
Tue, 4 Oct 22
59/71

Comments: 19 pages, 9 figures, 2 tables. Comments are welcome!

Estimate of spot size of a flat top beam in detection of gravitational waves in space [IMA]

http://arxiv.org/abs/2210.00509


Motivated by the necessity of a high-quality stray light control in the detection of the gravitational waves in space, the spot size of a flat top beam generated by the clipping of the Gaussian beam(GB) is studied. By adopting the mode expansion method (MEM) approach to simulating the beam, a slight variant of the definition of the mean square deviation (MSD) spot size for the MEM beam is proposed and this enables us to quickly estimate the spot size for arbitrary propagation distance. Given that the degree of clipping is dependent on the power ratio within the surface of an optical element, the power ratio within the MSD spot range is used as a measure of spot size. The definition is then validated in the cases of simple astigmatic Gaussian beam and nearly-Gaussian beam profiles. As a representative example, the MSD spot size for a top-hat beam in a science interferometer in the detection of gravitational waves in space is then simulated. As in traditional MSD spot size analysis, the spot size is divergent when diffraction is taken into account. A careful error analysis is carried out on the divergence and in the present context, it is argued that this error will have little effect on our estimation. Using the results of our study allows an optimal design of optical systems with top-hat or other types of non-Gaussian beams. Furthermore, it allows testing the interferometry of space-based gravitational wave detectors for beam clipping in optical simulations. The present work will serve as a useful guide in the future system design of the optical bench and the sizes of the optical components.

Read this paper on arXiv…

Z. Hao, T. Haase, H. Jin, et. al.
Tue, 4 Oct 22
61/71

Comments: 28 pages, 12 figures

Constraints on the scalar-field potential in warm inflation [CL]

http://arxiv.org/abs/2209.14908


We quantify the degree of fine tuning required to achieve an observationally viable period of inflation in the strongly dissipative regime of warm inflation. The “fine-tuning” parameter $\lambda$ is taken to be the ratio of the change in the height of the potential $\Delta V$ to the change in the scalar field $(\Delta \phi)^{4}$, i.e. the width of the potential, and therefore measures the requisite degree of flatness in the potential. The best motivated warm inflationary scenarios involve a dissipation rate of the kind $\Gamma\propto T^c$ with $c\geq 0$, and for all such cases, the bounds on $\lambda$ are tighter than those for standard cold inflation by at least 3 orders of magnitude. In other words, these models require an even flatter potential than standard inflation. On the other hand for the case of warm inflation with $c< 0$, we find that in a strongly dissipative regime the bound on $\lambda$ can significantly weaken with respect to cold inflation. Thus, if a warm inflation model can be constructed in a strongly dissipative, negatively temperature-dependent regime, it accommodates steeper potentials otherwise ruled out in standard inflation.

Read this paper on arXiv…

G. Montefalcone, V. Aragam, L. Visinelli, et. al.
Mon, 3 Oct 22
3/55

Comments: 6 pages, Preprint Numbers: UTWI-03-2022, NORDITA 2022-068

Galaxy Distributions as Fractal Systems [CEA]

http://arxiv.org/abs/2209.15044


This paper discusses if large scale galaxy distribution samples containing almost one million objects can be characterized as fractal systems. The analysis performed by Teles et al. (2021; arXiv:2012.07164) on the UltraVISTA DR1 survey is extended here to the SPLASH and COSMOS2015 catalogs, hence adding 750k new galaxies with measured redshifts to the studied samples. The standard $\Lambda$CDM cosmology having $H_0=(70\pm5)$ km/s/Mpc and number density tools required for describing these galaxy distributions as single fractal systems with dimension $D$ are adopted. We use the luminosity distance $d_L$, redshift distance $d_z$ and galaxy area distance (transverse comoving distance) $d_G$ as relativistic distance definitions to derive galaxy number densities in the redshift interval $0.1\le z\le4$ at volume limited subsamples defined by absolute magnitudes in the K-band. Similar to the findings of Teles et al. (2021; arXiv:2012.07164), the results show two consecutive redshift scales where galaxy distribution data behave as single fractal structures. For $z<1$ we found $D=1.00\pm0.12$ for the SPLASH galaxies, and $D=1,39\pm0.19$ for the COSMOS2015. For $1\le z\le4$ we respectively found $D=0.83^{+0.36}{-0.37}$ and $D=0.54^{+0.27}{-0.26}$. These results were verified to be robust under the assumed Hubble constant uncertainty. Calculations considering blue and red galaxies subsamples in both surveys showed that the fractal dimensions of blue galaxies as basically unchanged, but the ones for the red galaxies changed mostly to smaller values, meaning that $D$ may be seen as a more intrinsic property of the distribution of objects in the Universe, therefore allowing for the fractal dimension to be used as a tool to study different populations of galaxies. All results confirm the decades old theoretical prediction of a decrease in the fractal dimension for $z>1$.

Read this paper on arXiv…

S. Teles, A. Lopes and M. Ribeiro
Mon, 3 Oct 22
5/55

Comments: 14 pages, 15 figures, 43 graphs, 6 tables. LaTeX. Accepted for publication in the “European Physical Journal C”

SCoRe: A New Framework to Study Unmodeled Physics from Gravitational Wave Data [CL]

http://arxiv.org/abs/2209.14321


A confident discovery of physics beyond what has been consistently modeled from gravitational wave (GW) data requires a technique that can distinguish between noise artifacts and unmodeled signatures while also shedding light on the underlying physics. We propose a new data analysis method, \texttt{SCoRe} (Structured Correlated Residual), to search for unmodeled physics in the GW data which can cover both of these aspects. The method searches for structure in the cross-correlation power spectrum of the residual strain between pairs of GW detectors. It does so by projecting this power spectrum onto a frequency-dependent template. The template may be model-independent or model-dependent and is constructed based on the properties of the GW source parameters. The projection of the residual strain enables the distinction between noise artifacts and any true signal while capturing possible dependence on the GW source parameters. Our method is constructed in a Bayesian framework and we have shown its application on a model-independent toy example and for a model motivated by an effective field theory of gravity. The method developed here will be useful to search for a large variety of new physics and yet-to-be-modeled known physics in the GW data accessible from the current network of LIGO-Virgo-KAGRA detectors and from future earth- and space-based GW detectors such as A+, LISA, Cosmic Explorer, and Einstein Telescope.

Read this paper on arXiv…

G. Dideron, S. Mukherjee and L. Lehner
Mon, 3 Oct 22
9/55

Comments: 18 pages, 9 figures

Parity violating gravitational waves at the end of inflation [CL]

http://arxiv.org/abs/2209.15572


Inflaton-vector interactions of the type $\phi F\tilde{F}$ have provided interesting phenomenology to tackle some of current problems in cosmology, namely the vectors could constitute the dark matter component. It could also lead to possible signatures imprinted in a gravitational wave spectrum. Through this coupling, a rolling inflaton induces an exponential production of the transverse polarizations of the vector field, having a maximum at the end of inflation when the inflaton field velocity is at its maximum. These gauge particles, already parity asymmetric, will source the tensor components of the metric perturbations, leading to the production of parity violating gravitational waves. In this work we examine the vector particle production with an attempt to mimic its backreaction effects on the inflation evolution in the weak coupling regime. Furthermore, we fully integrate the gauge particle amplitudes spectrum during this production epoch, studying the behavior until the end of reheating. Finally, we calculate the gravitational wave spectrum solely relying on the vector mode WKB expansion in its regime of validity.

Read this paper on arXiv…

M. Bastero-Gil and A. Manso
Mon, 3 Oct 22
37/55

Comments: 17 pages, 8 figures

New Perspectives on Spontaneous Scalarization in Black Holes and Neutron Stars [CL]

http://arxiv.org/abs/2209.15330


Although general relativity passes all precision tests to date, there are several reasons to go beyond the current model of gravitation and search for new fundamental physics. This means looking for new, so far undetected, fields. Scalars are the easiest fields to consider and they are ubiquitous in both extensions of the Standard Model and in alternative theories of gravity. That is why a lot of attention has been drawn towards the investigation of scalar-tensor theories, where gravity is described by both the metric tensor and a scalar field.
A particularly interesting phenomenon that has recently gained increasing interest is spontaneous scalarization. In gravity theories that exhibit this mechanism, astrophysical objects are identical to their general relativistic counterpart until they reach a specific threshold, usually either in compactness, curvature or, as recently shown, in spin. Beyond this threshold, they acquire a nontrivial scalar configuration, which also affects their structure.
In this thesis, we focus on the study of this mechanism in generalized scalar-tensor theories. We identify a minimal action that contains all of the terms that can potentially trigger spontaneous scalarization. We first focus on the onset of scalarization in this specific theory and determine the relevant thresholds in terms of the contributing coupling constants and the properties of the compact object. Finally, we study the effect of this model on the properties of both scalarized black holes and neutron stars, such as affecting their domain of existence or the amount of scalar charge they carry.

Read this paper on arXiv…

G. Ventagli
Mon, 3 Oct 22
50/55

Comments: 134 pages, PhD Thesis

Result of the MICROSCOPE Weak Equivalence Principle test [CL]

http://arxiv.org/abs/2209.15488


The space mission MICROSCOPE dedicated to the test of the Equivalence Principle (EP) operated from April 25, 2016 until the deactivation of the satellite on October 16, 2018. In this analysis we compare the free-fall accelerations ($a_{\rm A}$ and $a_{\rm B}$) of two test masses in terms of the E\”otv\”os parameter $\eta({\rm{A, B}}) = 2 \frac{a_{\rm A}- a_{\rm B}}{a_{\rm A}+ a_{\rm B}}$. No EP violation has been detected for two test masses, made from platinum and titanium alloys, in a sequence of 19 segments lasting from 13 to 198 hours down to the limit of the statistical error which is smaller than $10^{-14}$ for $ \eta({\rm{Ti, Pt}})$. Accumulating data from all segments leads to $\eta({\rm{Ti, Pt}}) =[-1.5\pm{}2.3{\rm (stat)}\pm{}1.5{\rm (syst)}] \times{}10^{-15}$ showing no EP violation at the level of $2.7\times{}10^{-15}$ if we combine stochastic and systematic errors quadratically. This represents an improvement of almost two orders of magnitude with respect to the previous best such test performed by the E\”ot-Wash group. The reliability of this limit has been verified by comparing the free falls of two test masses of the same composition (platinum) leading to a null E\”otv\”os parameter with a statistical uncertainty of $1.1\times{}10^{-15}$.

Read this paper on arXiv…

P. Touboul, G. Métris, M. Rodrigues, et. al.
Mon, 3 Oct 22
53/55

Comments: Class. Quantum Grav. 39 204009

The Interplay between the Dark Matter Axion and Primordial Black Holes [CEA]

http://arxiv.org/abs/2209.14307


We show that the relic abundance and expected mass range of the QCD axion, a hypothetical particle that can potentially constitute the cosmic dark matter (DM), are greatly modified if the axion field resulting from the evaporation of primordial black holes (PBHs) begins to oscillate just before the onset of Big Bang Nucleosynthesis (BBN). We predominantly explore the PBHs in the mass range $(10^6 – 5\times 10^8)\,$g. We investigate the relation between the relic abundance of DM axion and the primordial population of black holes. We numerically solve the set of Boltzmann equations that governs the cosmological evolution during the radiation bath and the PBH-dominated epoch, providing the bulk energy content of the early Universe. We further solve the equation of motion of the axion field in addition to obtaining its present abundance. If the QCD axion is ever discovered, it will give us insights into the early Universe and probe into the physics of the PBH-dominated era. Light QCD axions, alongside non-relativistic particles, are generated from PBHs evaporation through Hawking radiation and could make up a fraction of dark radiation (DR). We estimate the bounds on the model from DR axions produced via said PBH evaporation and thermal decoupling, and we account for isocurvature bounds during the period of inflation where the Peccei-Quinn symmetry is broken. We, additionally, take the results obtained and put them against the available CMB data and state our observations. We briefly study the forecasts from gravitational wave searches. We comment on the consequences of PBH accretion and on the uncertainties it may further add to particle physics modeling.

Read this paper on arXiv…

K. Mazde and L. Visinelli
Fri, 30 Sep 22
13/71

Comments: 16 pages, 4 figures

On the adiabatic subtraction of cosmological perturbations [CL]

http://arxiv.org/abs/2209.14362


Adiabatic subtraction is a popular method of renormalization of observables in quantum field theories on a curved spacetime. When applied to the computation of the power spectra of light ($m\ll H$) fields on de Sitter space with flat Friedmann-Lema\^{i}tre-Robertson-Walker slices, the standard prescriptions of adiabatic subtraction, traceable back to Parker’s work, lead to results that are significantly different from the standard predictions of inflation not only in the ultraviolet ($k\gg aH$) but also at intermediate ($m\ll k/a\lesssim H$) wavelengths. In this paper we review those results and we contrast them with the power spectra obtained using an alternative prescription for adiabatic subtraction applied to quantum field theoretical systems by Dabrowski and Dunne. This prescription eliminates the intermediate-wavelength effects of renormalization that are found when using the standard one.

Read this paper on arXiv…

S. Corbà and L. Sorbo
Fri, 30 Sep 22
14/71

Comments: 21 pages, 6 figures

Minimal model dependent constraints on cosmological nuisance parameters from combinations of cosmological data [CEA]

http://arxiv.org/abs/2209.14639


The study of cosmic expansion history and the late time cosmic acceleration from observational data depends on the nuisance parameters associated with the data. For example, the absolute peak magnitude of type Ia supernova associated with the type Ia supernova observations and the comoving sound horizon at the baryon drag epoch associated with baryon acoustic oscillation observations are two nuisance parameters. The nuisance parameters associated with the quasar and the gamma-ray bursts data are also considered. These nuisance parameters are constrained by combining the cosmological observations using the Gaussian process regression method without assuming any cosmological model or parametrization to the background cosmic expansion. The bounds obtained in this method can be used as the prior for the data analysis while considering the observational data accordingly. Interestingly, these bounds are independent of the present value of the Hubble parameter. Along with these nuisance parameters, the cosmic curvature density parameter is also constrained simultaneously and the constraints show no significant deviation from a flat Universe.

Read this paper on arXiv…

B. Dinda
Fri, 30 Sep 22
32/71

Comments: 8 pages, 3 figures, 3 tables; comments are welcome

The halo mass function and filaments in full cosmological simulations with fuzzy dark matter [CEA]

http://arxiv.org/abs/2209.14886


Fuzzy dark matter (FDM) is a dark matter candidate consisting of ultra-light scalar particles with masses around $10^{-22} \mathrm{eV}/c^2$, a regime where cold bosonic matter behaves as a collective wave rather than individual particles. It has increasingly attracted attention due to its rich phenomenology on astrophysical scales, with implications for the small-scale tensions present within the standard cosmological model, $\Lambda$CDM. Although constraints on FDM are accumulating in many different contexts, very few have been verified by self-consistent numerical simulations. We present new large numerical simulations of cosmic structure formation with FDM, solving the full Schr\”odinger-Poisson (SP) equations using the AxiREPO code, which implements a pseudo-spectral numerical method. Combined with our previous simulations, they allow us to draw a four-way comparison of matter clustering, contrasting results (such as power spectra) for each combination of initial conditions (FDM vs. CDM) and dynamics (SP vs. $N$-body). By disentangling the impact of initial conditions and non-linear dynamics, we can gauge the validity of approximate methods used in previous works, such as ordinary $N$-body simulations with an FDM initial power spectrum. Due to the comparatively large volume achieved in our FDM simulations, we are able to measure the FDM halo mass function from full wave simulations for the first time, and compare to previous results obtained using analytic or approximate approaches. We find that, due to the cut-off of small-scale power in the FDM power spectrum, haloes are linked via continuous, smooth, and dense filaments throughout the entire simulation volume (unlike for the standard $\Lambda$CDM power spectrum), posing significant challenges for reliably identifying haloes. We also investigate the density profiles of these filaments and compare to their CDM counterparts.

Read this paper on arXiv…

S. May and V. Springel
Fri, 30 Sep 22
33/71

Comments: 18 pages, 13 figures; submitted to MNRAS

Prompt Emission of Gamma-Ray Bursts in the High-density Environment of Active Galactic Nuclei Accretion Disks [HEAP]

http://arxiv.org/abs/2209.14308


Long and short gamma-ray bursts are traditionally associated with galactic environments, where circumburst densities are small or moderate (few to hundreds of protons per cubic cm). However, both are also expected to occur in the disks of Active Galactic Nuclei, where the ambient medium density can be much larger. In this work we study, via semi-analytical methods, the propagation of the GRB outflow, its interaction with the external material, and the ensuing prompt radiation. In particular, we focus on the case in which the external shock develops early in the evolution, at a radius that is smaller than the internal shock one. We find that bursts in such high density environments are likely characterized by a single, long emission episode that is due to the superposition of individual pulses, with a characteristic hard to soft evolution irrespective of the light curve luminosity. While multi-pulse light curves are not impossible, they would require the central engine to go dormant for a long time before re-igniting. In addition, short GRB engines would produce bursts with prompt duration that would exceed the canonical 2 s separation threshold and would likely be incorrectly classified as long events, even though they would not be accompanied by a simultaneous supernova. Finally, these events have a large dynamical efficiency which would produce a bright prompt emission followed by a somewhat dim afterglow.

Read this paper on arXiv…

D. Lazzati, G. Soares and R. Perna
Fri, 30 Sep 22
41/71

Comments: 9 pages, 5 figures, under review for AAS Journals

Probing Early Universe Supercooled Phase Transitions with Gravitational Wave Data [CL]

http://arxiv.org/abs/2209.14707


We investigate the reach of the LIGO/Virgo/KAGRA detectors in the search for signatures of first-order phase transitions in the early Universe. Utilising data from the first three observing runs, we derive constraints on the parameters of the underlying gravitational-wave background, focusing on transitions characterised by strong supercooling. As an application of our analysis, we determine bounds on the parameter space of two representative particle physics models. We also comment on the expected reach of third-generation detectors in probing supercooled phase transitions.

Read this paper on arXiv…

C. Badger, B. Fornal, K. Martinovic, et. al.
Fri, 30 Sep 22
45/71

Comments: 10 pages, 7 figures

Pulsar and cosmic variances of pulsar timing-array correlation measurements of the stochastic gravitational wave background [CL]

http://arxiv.org/abs/2209.14834


Pulsar timing-array correlation measurements offer an exciting opportunity to test the nature of gravity in the cosmologically novel nanohertz gravitational wave regime. The stochastic gravitational wave background is assumed Gaussian and random, while there are limited pulsar pairs in the sky. This brings theoretical uncertainties to the correlation measurements, namely the pulsar variance due to pulsar samplings and the cosmic variance due to Gaussian signals. We demonstrate a straightforward calculation of the mean and the variances on the Hellings-Downs correlation relying on a power spectrum formalism. We keep arbitrary pulsar distances and consider gravitational wave modes beyond Einstein gravity as well as off the light cone throughout, thereby presenting the most general and, most importantly, numerically efficient calculation of the variances.

Read this paper on arXiv…

R. Bernardo and K. Ng
Fri, 30 Sep 22
49/71

Comments: 18 pages, 6 figures, comments welcome

Vanishing of black hole tidal Love numbers from scattering amplitudes [CL]

http://arxiv.org/abs/2209.14324


We extract the black hole (BH) static tidal deformability coefficients (Love numbers) and their spin-0 and spin-1 analogs by comparing on-shell amplitudes for fields to scatter off a spinning BH in the worldline effective field theory (EFT) and in general relativity (GR). We point out that the GR amplitudes due to tidal effects originate entirely from the BH potential region. Thus, they can be separated from gravitational non-linearities in the wave region, whose proper treatment requires higher order EFT loop calculations. In particular, the elastic scattering in the near field approximation is produced exclusively by tidal effects. We find this contribution to vanish identically, which implies that the static Love numbers of Kerr BHs are zero for all types of perturbations. We also reproduce the known behavior of scalar Love numbers for higher dimensional BHs. Our results are manifestly gauge-invariant and coordinate-independent, thereby providing a valuable consistency check for the commonly used off-shell methods.

Read this paper on arXiv…

M. Ivanov and Z. Zhou
Fri, 30 Sep 22
50/71

Comments: 7 pages, 1 figure, comments are welcome

Testing gravitational wave propagation with multiband detections [CL]

http://arxiv.org/abs/2209.14398


Effective field theories (EFT) of dark energy (DE) — built to parameterise the properties of DE in an agnostic manner — are severely constrained by measurements of the propagation speed of gravitational waves (GW). However, GW frequencies probed by ground-based interferometers lie around the typical strong coupling scale of the EFT, and it is likely that the effective description breaks down before even reaching that scale. We discuss how this leaves the possibility that an appropriate ultraviolet completion of DE scenarios, valid at scales beyond an EFT description, can avoid present constraints on the GW speed. Instead, additional constraints in the lower frequency LISA band would be harder to escape, since the energies involved are orders of magnitude lower. By implementing a method based on GW multiband detections, we show indeed that a single joint observation of a GW150914-like event by LISA and a terrestrial interferometer would allow one to constrain the speed of light and gravitons to match to within $10^{-15}$. Multiband GW observations can therefore firmly constrain scenarios based on the EFT of DE, in a robust and unambiguous way.

Read this paper on arXiv…

T. Baker, E. Barausse, A. Chen, et. al.
Fri, 30 Sep 22
55/71

Comments: 11 pages, 4 figures

On the dynamics of a dark sector coupling [CEA]

http://arxiv.org/abs/2209.14816


Interacting dark energy models may play a crucial role in explaining several important observational issues in modern cosmology and also may provide a solution to current cosmological tensions. Since the phenomenology of the dark sector could be extremely rich, one should not restrict the interacting models to have a coupling parameter which is constant in cosmic time, rather allow for its dynamical behavior, as it is common practice in the literature when dealing with other dark energy properties, as the dark energy equation of state. We present here a compendium of the current cosmological constraints on a large variety of interacting models, investigating scenarios where the coupling parameter of the interaction function and the dark energy equation of state can be either constant or dynamical. For the most general schemes, in which both the coupling parameter of the interaction function and the dark energy equation of state are dynamical, we find $95\%$~CL evidence for a dark energy component at early times and slightly milder evidence for a dynamical dark coupling for the most complete observational data set exploited here, which includes CMB, BAO and Supernova Ia measurements. Interestingly, there are some cases where a dark energy component different from the cosmological constant case at early times together with a coupling different from zero today, can alleviate both the $H_0$ and $S_8$ tension for the full dataset combination considered here. Due to the energy exchange among the dark sectors, the current values of the matter energy density and of the clustering parameter $\sigma_8$ are shifted from their $\Lambda$CDM-like values. This fact makes future surveys, especially those focused on weak lensing measurements, unique tools to test the nature and the couplings of the dark energy sector.

Read this paper on arXiv…

W. Yang, S. Pan, O. Mena, et. al.
Fri, 30 Sep 22
61/71

Comments: 26 pages, 21 tables and 8 figures; comments are welcome

The Effect of Light Deflection by Solar System Objects on High-Precision SKA Astrometry [CL]

http://arxiv.org/abs/2209.08702


We have computed the deflection angles caused by 195 objects in the solar system, including 177 satellites and eight asteroids. Twenty-one satellites and six asteroids can bend light from distant compact extragalactic sources by more than 0.1 $\mu$as, and fourteen satellites and the asteroid Ceres can deflect light by more than 1.0 $\mu$as. We calculated the zones and durations of perturbations posed by the gravitational fields of five planets (excluding Earth, Jupiter, and Saturn), Pluto, and Ceres, where the perturbations would affect astrometry measured with the Squared Kilometre Array (SKA). Perturbed zones with deflection angles larger than 0.1 and 1.0 $\mu$as appear as ribbons. Their widths range from dozens of degrees for Uranus, Neptune, and Venus to several degrees or less for other objects at 0.1 $\mu$as, and from $\sim$ 16$^{\circ}$ for Venus to several degrees or less for other objects at 1.0 $\mu$as. From the calculated perturbation durations, the influence of the gravitational fields of selected objects can be divided into four levels: hardly affect SKA astrometry (I), may have little effect (II), may have a great effect (III) on single-epoch astrometry, and may greatly affect both single- and multi-epoch astrometry (IV). The objects corresponding to these levels are Ceres (I), Pluto (II), Mercury and Mars (III), and other objects (IV).

Read this paper on arXiv…

Y. Li, Y. Xu, S. Bian, et. al.
Thu, 29 Sep 22
3/70

Comments: 10 figures, 5 tables, accepted by ApJ

Prospects for LISA to detect a gravitational-wave background from first order phase transitions [CL]

http://arxiv.org/abs/2209.13277


First order phase transitions in the early universe could produce a gravitational-wave background that might be detectable by the Laser Interferometer Space Antenna (LISA). Such an observation would provide evidence for physics beyond the Standard Model. We study the ability of LISA to observe a gravitational-wave background from phase transitions in the presence of an extragalactic foreground from binary black hole mergers throughout the universe, a galactic foreground from white dwarf binaries, and LISA noise. Modelling the phase transition gravitational wave background as a double broken power law, we use the deviance information criterion as a detection statistic, and Fisher matrix and Markov Chain Monte Carlo methods to assess the measurement accuracy of the parameters of the power spectrum. While estimating all the parameters associated with the gravitational-wave backgrounds, foregrounds, and LISA noise, we find that LISA could detect a gravitational-wave background from phase transitions with a peak frequency of 1 mHz and normalized energy density amplitude of $\OmPeak \simeq 3 \times 10^{-11}$. With $\OmPeak \simeq 10^{-10}$, the signal is detectable if the peak frequency is in the range $4 \times 10^{-4}$ to $9 \times 10^{-3}$ Hz, and the peak amplitude and frequency can be estimated to an accuracy of 10\% to 1\%.

Read this paper on arXiv…

G. Boileau, N. Christensen, C. Gowling, et. al.
Thu, 29 Sep 22
4/70

Comments: N/A

Inspiral gravitational waveforms from compact binary systems in Horndeski gravity [CL]

http://arxiv.org/abs/2209.13749


In a subclass of Horndeski theories with the speed of gravity equivalent to that of light, we study gravitational radiation emitted during the inspiral phase of compact binary systems. We compute the waveform of scalar perturbations under a post-Newtonian expansion of energy-momentum tensors of point-like particles that depend on a scalar field. This scalar mode not only gives rise to breathing and longitudinal polarizations of gravitational waves, but it is also responsible for scalar gravitational radiation in addition to energy loss associated with transverse and traceless tensor polarizations. We calculate the Fourier-transformed gravitational waveform of two tensor polarizations under a stationary phase approximation and show that the resulting waveform reduces to the one in a parametrized post-Einsteinian (ppE) formalism. The ppE parameters are directly related to a scalar charge in the Einstein frame, whose existence is crucial to allow the deviation from General Relativity (GR). We apply our general framework to several concrete theories and show that a new theory of spontaneous scalarization with a higher-order scalar kinetic term leaves interesting deviations from GR that can be probed by the observations of gravitational waves emitted from neutron star-black hole binaries. If the scalar mass exceeds the order of typical orbital frequencies $\omega \simeq 10^{-13}$ eV, which is the case for a recently proposed scalarized neutron star with a self-interacting potential, the gravitational waveform practically reduces to that in GR.

Read this paper on arXiv…

Y. Higashino and S. Tsujikawa
Thu, 29 Sep 22
9/70

Comments: 30 pages, 2 figures

Simulating the inflationary Universe: from single-field to the axion-U(1) model [CEA]

http://arxiv.org/abs/2209.13616


We present a nonlinear study of the inflationary epoch based on numerical lattice simulations. Lattice simulations are a well-known tool in primordial cosmology, and they have been extensively used to study the reheating epoch after inflation. We generalize this known machinery to the inflationary epoch. Being this the first simulation of the inflationary epoch much before the end of inflation, the first part of the thesis focuses on the minimal single-field model of inflation. We discuss the conceptual and technical ingredients needed to simulate inflation on a lattice. The simulation is used to reproduce the nearly scale-invariant spectrum of scalar perturbations, as well as the oscillations in the power spectrum caused by a step in the potential. In the second part, we focus on the more complicated axion-U(1) model of inflation and present the first lattice simulation of this model during the deep inflationary epoch. We use the simulation to discover new properties of primordial scalar perturbations from this model. In the linear regime of the theory, we find high-order non-Gaussianity (beyond trispectrum) to be key to describing the statistical properties of scalar perturbations. Conversely, we find perturbations to be nearly Gaussian in the nonlinear regime of the theory. This relaxes existing constraints from the overproduction of primordial black holes, allowing for a gravitational waves signal in the observable range of upcoming experiments such as LISA. Our results show that lattice simulations can be a powerful tool to study the inflationary epoch and its observational signatures.

Read this paper on arXiv…

A. Caravano
Thu, 29 Sep 22
36/70

Comments: PhD thesis; 111 pages; Papers associated: arXiv:2102.06378, arXiv:2110.10695, arXiv:2204.12874

DVGAN: Stabilize Wasserstein GAN training for time-domain Gravitational Wave physics [IMA]

http://arxiv.org/abs/2209.13592


Simulating time-domain observations of gravitational wave (GW) detector environments will allow for a better understanding of GW sources, augment datasets for GW signal detection and help in characterizing the noise of the detectors, leading to better physics. This paper presents a novel approach to simulating fixed-length time-domain signals using a three-player Wasserstein Generative Adversarial Network (WGAN), called DVGAN, that includes an auxiliary discriminator that discriminates on the derivatives of input signals. An ablation study is used to compare the effects of including adversarial feedback from an auxiliary derivative discriminator with a vanilla two-player WGAN. We show that discriminating on derivatives can stabilize the learning of GAN components on 1D continuous signals during their training phase. This results in smoother generated signals that are less distinguishable from real samples and better capture the distributions of the training data. DVGAN is also used to simulate real transient noise events captured in the advanced LIGO GW detector.

Read this paper on arXiv…

T. Dooney, S. Bromuri and L. Curier
Thu, 29 Sep 22
45/70

Comments: 10 pages, 6 figures, 3 tables

Primordial black holes and gravitational waves induced by exponential-tailed perturbations [CEA]

http://arxiv.org/abs/2209.13891


Primordial black holes (PBHs) whose masses are in $\sim[10^{-15}M_\odot,10^{-11}M_{\odot}]$ have been extensively studied as a candidate of whole dark matter (DM). One of the probes to test such a PBH-DM scenario is scalar-induced stochastic gravitational waves (GWs) accompanied with the enhanced primordial fluctuations to form the PBHs with frequency peaked in the mHz band being targeted by the LISA mission. In order to utilize the stochastic GWs for checking the PBH-DM scenario, it needs to exactly relate the PBH abundance and the amplitude of the GWs spectrum. Recently in Kitajima et al., the impact of the non-Gaussianity of the enhanced primordial curvature perturbations on the PBH abundance has been investigated based on the peak theory, and they found that a specific non-Gaussian feature called the exponential tail significantly increases the PBH abundance compared with the Gaussian case. In this work, we investigate the spectrum of the induced stochastic GWs associated with PBH DM in the exponential-tail case. In order to take into account the non-Gaussianity properly, we employ the diagrammatic approach for the calculation of the spectrum. We find that the amplitude of the stochastic GW spectrum is slightly lower than the one for the Gaussian case, but it can still be detectable with the LISA sensitivity. We also find that the non-Gaussian contribution can appear on the high-frequency side through their complicated momentum configurations. Although this feature emerges under the LISA sensitivity, it might be possible to obtain information about the non-Gaussianity from GW observation with a deeper sensitivity such as the DECIGO mission.

Read this paper on arXiv…

K. Abe, R. Inui, Y. Tada, et. al.
Thu, 29 Sep 22
53/70

Comments: 33 pages, 19 figures

Primordial Black Hole Formation in Starobinsky's Linear Potential Model [CEA]

http://arxiv.org/abs/2209.14183


We study the power spectrum of the comoving curvature perturbation $\cal R$ in the model that glues two linear potentials of different slopes, originally proposed by Starobinsky. We find that the enhanced power spectrum reaches its maximum at the wavenumber which is $\pi$ times the junction scale. The peak is $\sim2.61$ times larger than the ultraviolet plateau. We also show that its near-peak behavior can be well approximated by a constant-roll model, once we define the effective ultra-slow-roll $e$-folding number appropriately by considering the contribution from non-single-clock phase only. Such an abrupt transition to non-attractor phase can leave some interesting characteristic features in the energy spectrum of the scalar-induced gravitational waves, which are detectable in the space-borne interferometers if the primordial black holes generated at such a high peak are all the dark matter.

Read this paper on arXiv…

S. Pi and J. Wang
Thu, 29 Sep 22
65/70

Comments: 45 pages, 8 figures

A light in the dark: searching for electromagnetic counterparts to black hole-black hole mergers in LIGO/Virgo O3 with the Zwicky Transient Facility [HEAP]

http://arxiv.org/abs/2209.13004


The accretion disks of active galactic nuclei (AGN) are promising locations for the merger of compact objects detected by gravitational wave (GW) observatories. Embedded within a baryon-rich, high density environment, mergers within AGN are the only GW channel where an electromagnetic (EM) counterpart must occur (whether detectable or not). Considering AGN with unusual flaring activity observed by the Zwicky Transient Facility (ZTF), we describe a search for candidate EM counterparts to binary black hole (BBH) mergers detected by LIGO/Virgo in O3. After removing probable false positives, we find nine candidate counterparts to BBH mergers mergers during O3 (seven in O3a, two in O3b) with a $p$-value of 0.019. Based on ZTF sky coverage, AGN geometry, and merger geometry, we expect $\approx 3(N_{\rm BBH}/83)(f_{\rm AGN}/0.5)$ potentially detectable EM counterparts from O3, where $N_{\rm BBH}$ is the total number of observed BBH mergers and $f_{\rm AGN}$ is the fraction originating in AGN. Further modeling of breakout and flaring phenomena in AGN disks is required to reduce our false positive rate. Two of the events are also associated with mergers with total masses $> 100M_\odot$, which is the expected rate for O3 if hierarchical (large mass) mergers occur in the AGN channel. Candidate EM counterparts in future GW observing runs can be better constrained by coverage of the Southern sky as well as spectral monitoring of unusual AGN flaring events in LIGO/Virgo alert volumes. A future set of reliable AGN EM counterparts to BBH mergers will yield an independent means of measuring cosmic expansion ($H_0$) as a function of redshift.

Read this paper on arXiv…

M. Graham, B. McKernan, K. Ford, et. al.
Wed, 28 Sep 22
16/89

Comments: 24 pages, 6 figures, submitted to ApJ

Tests of Loop Quantum Gravity from the EHT Results of Sgr A$^*$ [CL]

http://arxiv.org/abs/2209.12584


The Event Horizon Telescope (EHT) collaboration’s image of the compact object at the galactic centre is the first direct evidence of the supermassive black hole Sgr A$^$. The shadow of Sgr A$^$ has an angular diameter $d_{sh}= 48.7 \pm 7\,\mu$as with fractional deviation from the Schwarzschild black hole shadow diameter $\delta= -0.08^{+0.09}{-0.09}\,,-0.04^{+0.09}{-0.10}$ (for the VLTI and Keck mass-to-distance ratios). Sgr A$^$’s shadow size is within $~10\%$ of the Kerr predictions, equipping us with yet another tool to analyse the gravity in the strong-field regime, including testing loop quantum gravity (LQG). We use Sgr A$^$’s shadow to constrain the metrics of two well-motivated LQG-inspired rotating black holes (LIRBHs) models characterized by an additional deviation parameter $L_q$, which recover the Kerr spacetime in the absence of quantum effects ($L_q \to 0$). We use the astrophysical observables shadow area $A$ and oblateness $D$ to estimate the black hole parameters. When increasing the size of the quantum effects through $L_q$, the black hole shadow size increases monotonically, while the shape gets more distorted, allowing us to constrain the fundamental parameter $L_q$. While the EHT observational results completely rule out the wormhole region in the second LIRBH, a substantial parameter region of the generic black holes in both models agree with the EHT results. We find upper bounds on $L_q$ from the shadow of Sgr A$^$: $L_q \lesssim 0.0423$ and $L_q \lesssim 0.0821$ for the two LIRBHs respectively, both more stringent than those obtained with the EHT image of M87$^$.

Read this paper on arXiv…

M. Afrin and S. Ghosh
Wed, 28 Sep 22
18/89

Comments: 15 pages, 6 figures, 1 table

Testing Rotating Regular Metrics with EHT Results of Sgr A* [CL]

http://arxiv.org/abs/2207.00078


The Event Horizon Telescope (EHT) observation unveiled the first image of supermassive black hole Sgr A* showing a shadow of diameter $\theta_{sh}= 48.7 \pm 7\,\mu$as with fractional deviation from the Schwarzschild black hole shadow diameter $\delta = -0.08^{+0.09}{-0.09}~\text{(VLTI)},-0.04^{+0.09}{-0.10}~\text{(Keck)}$. The Sgr A* shadow size is within $~10\%$ of the Kerr predictions, providing us with another tool to investigate the nature of strong-field gravity. We use the Sgr A* shadow observables to constrain metrics of four independent and well-motivated, parametrically different from Kerr spacetime, rotating regular spacetimes, and the corresponding no-horizon spacetimes. We present constraints on the deviation parameter $g$ of rotating regular black holes. The shadow angular diameter $\theta_{sh}$ within $1 \sigma$ region, places bounds on the parameters $a$ and $g$. Together with EHT bounds on $\theta_{sh}$ and $\delta$ of Sgr A*, our analysis concludes that the three rotating regular black holes, viz., Bardeen Hayward, and Simpson-Visser black holes, and corresponding no-horizon spacetimes agree with the EHT results of Sgr A*. Thus, these three rotating regular spacetimes and Kerr black holes are indiscernible in some parameter space, and one can not rule out the possibility of the former being strong candidates for astrophysical black holes.

Read this paper on arXiv…

R. Walia, S. Ghosh and S. Maharaj
Wed, 28 Sep 22
46/89

Comments: 21 pages, 16 figures and 1 table. Accepted for publication in the Astrophysical Journal

A Forecast for Large Scale Structure Constraints on Horndeski Gravity with Line Intensity Mapping [CEA]

http://arxiv.org/abs/2209.13029


We consider the potential for line intensity mapping (LIM) of the rotational CO(1-0), CO(2-1) and CO(3-2) transitions to detect deviations from General Relativity from $0 < z < 3$ within the framework of a very general class of modified gravity models, called Horndeski theories. Our forecast assumes a multi-tracer analysis separately obtaining information from the matter power spectrum and the first two multipoles of the redshift space distortion power spectrum. To achieve $\pm 0.1$ level constraints on the slope of the kinetic gravity braiding and Planck mass evolution parameters, a mm-wave LIM experiment would need to accumulate $\approx 10^8-10^9$ spectrometer hours, feasible with instruments that could be deployed in the 2030s. Such a measurement would constrain large portions of the remaining parameter space available to Scalar-Tensor modified gravity theories. Our modeling code is publicly available.

Read this paper on arXiv…

B. Scott, K. Karkare and S. Bird
Wed, 28 Sep 22
58/89

Comments: 13 pages, 5 figures; to be submitted to Monthly Notices of the Royal Astronomical Society

The impact of confusion noise on golden binary neutron-star events in next-generation terrestrial observatories [CL]

http://arxiv.org/abs/2209.13452


Next-generation terrestrial gravitational-wave observatories will detect $\mathcal{O}(10^{5})$ signals from compact binary coalescences every year. These signals can last for several hours in the detectors’ sensitivity band and they will be affected by multiple unresolved sources contributing to a confusion-noise background in the data. Using an information-matrix formalism, we estimate the impact of the confusion noise power spectral density in broadening the parameter estimates of a GW170817-like event. If our estimate of the confusion noise power spectral density is neglected, we find that masses, spins, and distance are biased in about half of our simulations under realistic circumstances. The sky localization, while still precise, can be biased in up to $80\%$ of our simulations, potentially posing a problem in follow-up searches for electromagnetic counterparts.

Read this paper on arXiv…

L. Reali, A. Antonelli, R. Cotesta, et. al.
Wed, 28 Sep 22
59/89

Comments: 6 pages, 2 figures

Reconstructing physical parameters from template gravitational wave spectra at LISA: first order phase transitions [CEA]

http://arxiv.org/abs/2209.13551


A gravitational wave background from a first order phase transition in the early universe may be observable at millihertz gravitational wave (GW) detectors such as the Laser Interferometer Space Antenna (LISA). In this paper we introduce and test a method for investigating LISA’s sensitivity to gravitational waves from a first order phase transition using parametrised templates as an approximation to a more complete physical model. The motivation for developing the method is to provide a less computationally intensive way to perform Markov Chain Monte Carlo (MCMC) inference on the thermodynamic parameters of a first order phase transition, or on generally computationally intensive models. Starting from a map between the physical parameters and the parameters of an empirical template, we first construct a prior on the empirical parameters that contains the necessary information about the physical parameters; we then use the inverse mapping to reconstruct approximate posteriors on the physical parameters from a fast MCMC on the empirical template. We test the method on a double broken power law approximation to spectra in the sound shell model. The reconstruction method substantially reduces the proposal evaluation time, and despite requiring some precomputing of the mapping, this method is still cost-effective overall. In two test cases, with signal-to-noise $\sim 40$, the method recovers the physical parameters and the spectrum of the injected gravitational wave power spectrum to $95\%$ confidence. In previous Fisher matrix analysis we found the phase boundary speed $v_{\rm w}$ was expected to be the best constrained of the thermodynamic parameters. In this work, for an injected phase transition GW power spectrum with $v_{\rm w} = 0.55$, with a direct sample on the thermodynamic parameters we recover $0.630^{+0.17}{-0.059}$ and for our reconstructed sample $0.646^{+0.098}{-0.075}$.

Read this paper on arXiv…

C. Gowling, M. Hindmarsh, D. Hooper, et. al.
Wed, 28 Sep 22
61/89

Comments: N/A

Reconstruction of Power Spectrum of Primordial Curvature Perturbations on small scales from Primordial Black Hole Binaries scenario of LIGO/VIRGO detection [CEA]

http://arxiv.org/abs/2209.12911


As a candidate bound for the Binary Black Hole (BBH) merger events detected by LIGO/Virgo, Primordial Black Holes (PBHs) provide a useful tool to investigate the primordial curvature perturbations on small scales. Using the GWTC-1 to GWTC-3 catalogs, under the scenario that PBHs originate from large primordial curvature perturbations on small scales during inflationary epoch, we for the first time reconstruct the power spectrum of primordial curvature perturbations on small scales. It is found that the value of the amplitude of the primordial power spectrum is enhanced to $\mathcal{O}(10^{-2})$ on scales $\mathcal{O}(1)$ pc. This may imply the validity of PBH as a possible BBH merger candidate.

Read this paper on arXiv…

X. Wang, Y. Zhang, R. Kimura, et. al.
Wed, 28 Sep 22
69/89

Comments: 7 pages,5 figures