Testing Einstein's Equivalence Principle with Supercluster Laniakea's Gravitational Field

TL;DR

This study tests Einstein's Equivalence Principle by analyzing time delays of cosmic transients through the gravitational field of the Laniakea supercluster, achieving significantly tighter constraints than previous methods.

Contribution

The paper introduces a novel approach using the Laniakea supercluster's gravitational potential to improve EEP tests with cosmic transient data.

Findings

Constraints on EEP improved by 4-5 orders of magnitude.

Used photons from TeV blazars, gamma-ray bursts, and fast radio bursts.

Demonstrated the supercluster's gravitational field enhances EEP testing sensitivity.

Abstract

Comparing the parameterized post-Newtonian parameter $\gamma$ values for different types of particles, or the same type of particles with different energies is an important method to test the Einstein Equivalence Principle (EEP). Assuming that the observed time delays are dominated by the gravitational potential of the Laniakea supercluster of galaxies, better results of EEP constraints can be obtained. In this paper, we apply photons from three kinds of cosmic transients, including TeV blazars, gamma-ray bursts as well as fast radio bursts to constrain EEP. With a gravitational field far more stronger than a single galaxy, we obtain 4--5 orders of magnitude more stringent than the pervious results.