A Decisive test to confirm or rule out the existence of dark matter emulators using gravitational wave observations

TL;DR

This paper proposes a test using gravitational wave and electromagnetic observations to confirm or rule out dark matter emulators, a class of modified gravity theories, by detecting predicted time lags in signals from cosmic events.

Contribution

It introduces a method to distinguish dark matter emulators from standard models through measurable gravitational wave and photon time delays over cosmological distances.

Findings

Time lag for SN 1987a is days.

Time lag for GRB 070201 is about two years.

The method can decisively test dark matter emulator theories.

Abstract

We consider stable modified theories of gravity that reproduce galactic rotation curves and the observed amount of weak lensing without dark matter. In any such model gravity waves follow a different geodesic from that of other massless particles. For a specific class of models which we call "dark matter emulators," over cosmological distances this results in an easily detectable and difference between the arrival times of the pulse of gravity waves from some cosmic event and those of photons or neutrinos. For a repeat of SN 1987a (which took place in the Large Magellanic Cloud) the time lag is in the range of days. For the recent gamma ray burst, GRB 070201 (which seems to have taken place on the edge of the Andromeda galaxy) the time lag would be in the range of about two years.