Gravity Gets There First with Dark Matter Emulators

TL;DR

This paper explores how certain modified gravity theories, called Dark Matter Emulators, predict gravitational waves arrive before photons or neutrinos, offering potential observational tests for these models.

Contribution

It demonstrates that Dark Matter Emulators cause measurable differences in arrival times of gravitational waves and light, providing a novel way to test these theories against observations.

Findings

Gravitational waves arrive earlier than photons/neutrinos in these models.

Expected time lags vary depending on the source and dark matter profile.

Potential for observational verification with current and future detectors.

Abstract

We discuss the implications for gravity wave detectors of a class of modified gravity theories which dispense with the need for dark matter. These models, which are known as Dark Matter Emulators, have the property that weak gravitational waves couple to the metric that would follow from general relativity without dark matter whereas ordinary particles couple to a combination of the metric and other fields which reproduces the result of general relativity with dark matter. We show that there is an appreciable difference in the Shapiro delays of gravitational waves and photons or neutrinos from the same source, with the gravity waves always arriving first. We compute the expected time lags for GRB 070201, for SN 1987a, and for Sco-X1. We estimate the probable error by taking account of the uncertainty in position, and by using three different dark matter profiles.