Current and future constraints on cosmology and modified gravitational wave friction from binary black holes

Abstract

Gravitational wave (GW) standard sirens are well-established probes with which one can measure cosmological parameters, and are complementary to other probes like the cosmic microwave background (CMB) or supernovae standard candles. Here we focus on dark GW sirens, specifically binary black holes (BBHs) for which there is only GW data. Our approach relies on the assumption of a source-frame mass model for the BBH distribution, and we consider four models that are representative of the BBH population observed so far. In addition to inferring cosmological and mass model parameters, we use dark sirens to test modified gravity theories. These theories often predict different GW propagation equations on cosmological scales, leading to a different GW luminosity distance which in some cases can be parametrized by variables Ξ 0 and n. General relativity (GR) corresponds to Ξ 0 = 1. We perform a joint estimate of the population parameters governing mass, redshift, the variables characterizing the cosmology, and the modified GW luminosity distance. We use data from the third LIGO-Virgo-KAGRA observation run (O3) and find − for the four mass models and for three signal-to-noise ratio (SNR) cuts of 10, 11, 12 − that GR is consistently the preferred model to describe all observed BBH GW signals to date. Furthermore, all modified gravity parameters have posteriors that are compatible with the values predicted by GR at the 90% confidence interval (CI). We then focus on future observation runs O4 and O5, and for simplicity consider one specific mass model. We show that there are strong correlations between cosmological, astrophysical and modified gravity parameters. If GR is the correct theory of gravity, and assuming narrow priors on the cosmological parameters, we recover the modified gravity parameter Ξ 0 = 1.47 +0.92 −0.57 with O4, and Ξ 0 = 1.08 +0.27 −0.16 with O4 and O5. We also consider how wide priors on the cosmological parameters impact our results. If, however, Nature follows a modified gravity model with Ξ 0 = 1.8 and n = 1.91, we exclude GR at the 1.7 σ level with O4 and at the 2.3 σ level with O4 and O5 combined.

Gravitational wave constraints on spatial covariant gravities

“…where z is the redshift of the GW source and Ω Λ is the fractional dark energy density. If one considers the dark energy density as a constant, then one has [44] Ω…”

“…where Ω m (0) is the value of fractional energy density of matter. Several constraints on c M has been derived by using both the information of d gw L and d em L from GW events or populations [44][45][46]. Here we adopt a constraint in ref.…”

“…Here we adopt a constraint in ref. [44] from an jointed parameter estimation of the mass distribution, redshift evolution and GW friction with GWTC-3 for different BBH population models, which gives…”

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

“…Inference of the cosmological results using binary black holes (BBHs) will require understanding the dependencies on the astrophysical source parameters for different techniques such as statistical host identification (Schutz 1986;MacLeod & Hogan 2008;Del Pozzo 2012;Arabsalmani et al 2013;Gray et al 2020;Fishbach et al 2019;Abbott et al 2021a;Soares-Santos et al 2019;Finke et al 2021;Abbott et al 2020b;Palmese et al 2021), cross-correlation technique after taking into account GW source population uncertainty (Oguri 2016;Mukherjee & Wandelt 2018;Mukherjee et al 2020;Calore et al 2020;Mukherjee et al 2021a;Bera et al 2020;Scelfo et al 2020;Mukherjee et al 2021b;Cañas-Herrera et al 2021;Scelfo et al 2022;Cigarrán Díaz & Mukherjee 2022;Mukherjee et al 2022), or BBH massdistribution (Taylor et al 2012;Farr et al 2019;Mastrogiovanni et al 2021b;You et al 2021;Mancarella et al 2021;Mukherjee 2022;Leyde et al 2022;Ezquiaga & Holz 2022).…”

Prospects of testing late-time cosmology with weak lensing of gravitational waves and galaxy surveys

“…This results in a difference between the luminosity distance inferred from electromagnetic sources and the one inferred from the amplitude of GWs (see Sec. 3) [37][38][39] and can be used to test theories of gravity as shown in [37,38,[40][41][42][43][44][45].…”