[Submitted on 21 Oct 2022]

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

Submission history

From: Isabela Santiago De Matos [view email]

Fri, 21 Oct 2022 18:05:48 UTC (1,762 KB)

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