Gravitational Wave Opacity from Gauge Field Dark Energy [CL]

We show that astrophysical gravitational waves can undergo absorption and re-emission when propagating through cosmic gauge field dark energy. A sufficiently strong effect would impact the use of gravitational wave standard sirens to constrain the expansion history of the Universe. We investigate a particular model of dark energy based on a non-Abelian gauge field, and show that at early times it behaves like dark radiation, whereas a novel interaction causes it to drive cosmic acceleration at late times. Joint constraints on the cosmological scenario due to type 1a supernovae, baryon acoustic oscillations, and cosmic microwave background data are presented. We show that standard siren luminosity distances in the redshift range 0.5 < z < 1.5 would suffer at most a 1% absorption.

R. Caldwell and C. Devulder
Thu, 22 Feb 18
37/60

Comments: 16 pages, 19 figures

Gravitational Wave Emission from Collisions of Compact Scalar Solitons [CL]

We numerically investigate the gravitational waves generated by the head-on collision of equal-mass, self-gravitating, real scalar field solitons (oscillatons) as a function of their compactness $\mathcal{C}$. We show that there exist three different possible outcomes for such collisions: (1) an excited stable oscillaton for low $\mathcal{C}$, (2) a merger and formation of a black-hole for intermediate $\mathcal{C}$, and (3) a pre-merger collapse of both oscillatons into individual black-holes for large $\mathcal{C}$. For (1), the excited, aspherical oscillaton continues to emit gravitational waves. For (2), the total energy in gravitational waves emitted increases with compactness, and possesses a maximum which is greater than that from the merger of a pair of equivalent mass black-holes. The initial amplitudes of the quasi-normal modes in the post-merger ring-down in this case are larger than that of corresponding mass black-holes — potentially a key observable to distinguish black-hole mergers with their scalar mimics. For (3), the gravitational wave output is indistinguishable from a similar mass, black-hole–black-hole merger.

T. Helfer, E. Lim, M. Garcia, et. al.
Thu, 22 Feb 18
42/60

Comments: 8 Pages, 8 figures, movies : this https URL

Enhanced global signal of neutral hydrogen due to excess radiation at cosmic dawn [CEA]

We revisit the global 21cm signal calculation incorporating a possible radio background at early times, and find that the global 21cm signal shows a much stronger absorption feature, which could enhance detection prospects for future 21 cm experiments. In light of recent reports of a possible low-frequency excess radio background, we propose that detailed 21 cm calculations should include a possible early radio background.

C. Feng and G. Holder
Thu, 22 Feb 18
49/60

Comments: 4 pages, 4 figures

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SDSS-IV MaNGA: Modelling the metallicity gradients of gas and stars – radially dependent metal outflow vs IMF [GA]

J. Lian, D. Thomas, C. Maraston, et. al.
Wed, 21 Feb 18
1/58

Comments: 20 pages, 12 figures, accepted for publish on MNRAS

Constraints on Sub-GeV Dark Matter-Electron Scattering from the DarkSide-50 Experiment [CEA]

We present new constraints on sub-GeV dark matter particles scattering off electrons in argon based on an analysis of ionization signal data from the DarkSide-50 detector.

DarkSide. Collaboration, P. Agnes, I. Albuquerque, et. al.
Wed, 21 Feb 18
4/58

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Observational constraints on the free parameters of an interacting Bose-Einstein gas as a dark-energy model [CEA]

Dark energy is modelled by a Bose-Einstein gas of particles with an attractive interaction. It is coupled to cold dark matter, within a flat universe, for the late-expansion description, producing variations in particle-number densities. The model’s parameters, and physical association, are: $\Omega_{G0}$, $\Omega_{m0}$, the dark-energy rest-mass energy density and the dark-matter term scaling as a mass term, respectively; $\Omega_{i0}$, the self-interaction intensity; $x$, the energy exchange rate. Energy conservation relates such parameters. The Hubble equation omits $\Omega_{G0}$, but also contains $h$, the present-day expansion rate of the flat Friedman–Lem\^aitre–Robertson–Walker metric, and $\Omega_{b0}$, the baryon energy density, used as a prior. This results in the four effective chosen parameters $\Omega_{b0}$, $h$, $\Omega_{m0}$, $\Omega_{i0}$, fit with the Hubble expansion rate $H(z)$, and data from its value today, near distance, and supernovas. We derive wide $1\sigma$ and $2\sigma$ likelihood regions compatible with definite positive total CDM and IBEG mass terms. Additionally, the best-fit value of parameter $x$ relieves the coincidence problem, and a second potential coincidence problem related to the choice of $\Omega_{G0}$.

H. Lucatero–Villasenor, G. Izquierdo and J. Besprosvany
Wed, 21 Feb 18
11/58

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Primordial Black Hole Dark Matter and LIGO/Virgo Merger Rate from Inflation with Running Spectral Indices [CEA]

We study possibilities to explain the whole dark matter abundance by primordial black holes (PBHs) or to explain the merger rate of binary black holes estimated from the gravitational wave detections by LIGO/Virgo. We assume that the PBHs are originated in radiation- or matter-dominated era from large primordial curvature perturbation generated by inflation. We take a simple model-independent approach considering inflation with large running spectral indices which are parametrized by $n_\text{s}, \alpha_\text{s}$, and $\beta_\text{s}$ with being satisfying the observational bounds on them. The merger rate is fitted by PBHs with masses of $\mathcal{O}(10)$ $M_{\odot}$ produced in the radiation-dominated era. Then the running of running should be $\beta_\text{s} \sim 0.03$, which can be tested by future observation. On the other hand, the whole abundance of dark matter is consistent with PBHs with masses of asteroid ($\mathcal{O}(10^{-17})~M_{\odot}$) produced in an early matter-dominated era if a set of running parameters are properly realized.

K. Kohri and T. Terada
Wed, 21 Feb 18
13/58

Comments: 22 pages, 5 figures

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