# Gravitational waves: a new messenger to explore the universe

1 March 2021 to 9 April 2021
Institut Henri Poincaré
Europe/Paris timezone

## Mapping the inhomogeneous Universe with Standard Sirens: Degeneracy between inhomogeneity and modified gravity theories

Not scheduled
20m
Amphitheater Darboux (Institut Henri Poincaré)

### Amphitheater Darboux

#### Institut Henri Poincaré

11, Rue Pierre et Marie Curie 75005 Paris
Poster

### Description

The detection of gravitational waves (GWs) and an accompanying electromagnetic (E/M) counterpart have been suggested as a future probe for cosmology and theories of gravity. In this paper, we present calculations of the luminosity distance of sources taking into account inhomogeneities in the matter distribution that are predicted in numerical simulations of structure formation. In addition, we show that inhomogeneities resulting from clustering of matter can mimic certain classes of modified gravity theories, or other effects that dampen GW amplitudes, and deviations larger than $\delta \nu \sim \mathcal{O}(0.1)\ (99\%\ \rm{C.L.})$ to the extra friction term $\nu$, from zero, would be necessary to distinguish them. For these, we assume mock GWs sources, with known redshift, based on binary population synthesis models, between redshifts $z=0$ and $z=5$. We show that future GW detectors, like Einstein Telescope or Cosmic Explorer, will be needed for strong constraints on the inhomogeneity parameters and breaking the degeneracy between modified gravity effects and matter anisotropies by measuring $\nu$ at $5 \%$ and $1 \%$ level with $100$ and $350$ events respectively.

### Primary authors

Marios Kalomenopoulos (University of Edinburgh, Royal Observatory) Sadegh Khochfar (Royal Observatory Edinburgh) Jonathan Gair (Max Planck, Institute of Gravitational Physics, Potsdam) Shun Arai (Kyoto University)