Constraints on the distance duality relation with standard sirens

TL;DR

This paper forecasts how gravitational wave standard sirens, combined with supernovae and BAO data, can constrain violations of the distance duality relation, revealing potential false signals from modified gravity.

Contribution

It introduces a machine learning approach using Genetic Algorithms to forecast constraints on the electromagnetic and gravitational distance duality relation with GW data.

Findings

GW provide 3% constraints on DDR violation parameter.

GW constraints are comparable to BAO when combined with SNIa.

False detections of DDR violations could indicate modified gravity effects.

Abstract

We use gravitational wave (GW) standard sirens, in addition to Type Ia supernovae (SNIa) and baryon acoustic oscillation (BAO) mock data, to forecast constraints on the electromagnetic and gravitational distance duality relations (DDR). We make use of a parameterised approach based on a specific DDR violation model, along with a machine learning reconstruction method based on the Genetic Algorithms. We find that GW provide an alternative to the use of BAO data to constrain violations of the DDR, reaching $3\%$ constraints on the violation parameter we consider when combined with SNIa, which is only improved by a factor of $\approx1.4$ if one instead considers the combination of BAO and SNIa. We also investigate the possibility that a neglected modification of gravity might lead to a false detection of DDR violations, even when screening mechanisms are active. We find that such a false detection can be extremely significant, up to $\approx10\sigma$ for very extreme modified gravity scenarios, while this reduces to $\approx4\sigma$ in a more realistic case. False detections can also provide a smoking gun for the modified gravity mechanism at play, as a result of the tension introduced between the SNIa+GW and SNIa+BAO combinations.