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arXiv · 1712.08108

The gravitational-wave luminosity distance in modified gravity theories

Enis Belgacem·Yves Dirian·Stefano Foffa·Michele Maggiore
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Abstract

In modified gravity the propagation of gravitational waves (GWs) is in general different from that in general relativity. As a result, the luminosity distance for GWs can differ from that for electromagnetic signals, and is affected both by the dark energy equation of state $w_{\rm DE}(z)$ and by a function $\delta(z)$ describing modified propagation. We show that the effect of modified propagation in general dominates over the effect of the dark energy equation of state, making it easier to distinguish a modified gravity model from $\Lambda$CDM. We illustrate this using a nonlocal modification of gravity, that has been shown to fit remarkably well CMB, SNe, BAO and structure formation data, and we discuss the prospects for distinguishing nonlocal gravity from $\Lambda$CDM with the Einstein Telescope. We find that, depending on the exact sensitivity, a few tens of standard sirens with measured redshift at $z\sim 0.4$, or a few hundreds at $1 < z < 2$, could suffice.

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Enis Belgacem, Yves Dirian, Stefano Foffa, Michele Maggiore. 2017-12-21. The gravitational-wave luminosity distance in modified gravity theories. https://doi.org/10.1103/physrevd.97.104066

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