Constraining runaway dilaton models using joint gravitational-wave and electromagnetic observations

TL;DR

This paper investigates how joint gravitational-wave and electromagnetic observations can test and constrain dilaton models predicting variations in fundamental constants and deviations in cosmic distance measurements.

Contribution

It introduces a method to use multi-messenger observations to test dilaton models and constrain variations in Newton's constant relative to the fine-structure constant.

Findings

Next-generation detectors can constrain variations to a few parts in 100.

Application to GW170817 provides current bounds on model parameters.

Joint observations can distinguish between standard and modified gravity models.

Abstract

With the advent of gravitational-wave astronomy it has now been possible to constrain modified theories of gravity that were invoked to explain the dark energy. In a class of dilaton models, distances to cosmic sources inferred from electromagnetic and gravitational wave observations would differ due to the presence of a friction term. In such theories, the ratio of the Newton's constant to the fine structure constant varies with time. In this paper we explore the degree to which it will be possible to test such models. If collocated sources (e.g. supernovae and binary neutron star mergers), but not necessarily multimessengers, can be identified by electromagnetic telescopes and gravitational-wave detectors one can probe if light and gravitational radiation are subject to the same laws of propagation over cosmological distances. This helps in constraining the variation of Newton's constant relative to fine-structure constant. The next generation of gravitational wave detectors, such as the Cosmic Explorer and Einstein Telescope, in tandem with the Vera Rubin Observatory and gamma ray observatories such as the Fermi Space Observatory will be able to detect or constrain such variations at the level of a few parts in 100. We apply this method to GW170817 with distances inferred by the LIGO and Virgo detectors and the observed Kilonova.