Testing the equivalence principle on cosmological scales using the odd multipoles of galaxy cross-power spectrum and bispectrum

TL;DR

This paper proposes a novel method to test the equivalence principle on cosmological scales by analyzing odd multipoles of galaxy cross-power spectrum and bispectrum, focusing on non-standard matter fields.

Contribution

It introduces a new cosmological test for the equivalence principle using parity-violating relativistic effects in galaxy clustering data.

Findings

Relative velocity between galaxy components constrained to less than 28%.

Method demonstrates potential to detect violations of the equivalence principle on large scales.

Uses upcoming galaxy survey data for practical implementation.

Abstract

One of the cornerstones of general relativity is the equivalence principle. However, the validity of the equivalence principle has only been established on solar system scales for standard matter fields; this result cannot be assumed to hold for the non-standard matter fields that dominate the gravitational dynamics on cosmological scales. Here we show how the equivalence principle may be tested on cosmological scales for non-standard matter fields using the odd multipoles of the galaxy cross-power spectrum and bispectrum. This test makes use of the imprint on the galaxy cross-power spectrum and bispectrum by the parity-violating general relativistic deformations of the past-light cone, and assumes that galaxies can be treated as test particles that are made of baryons and cold dark matter. This assumption leads to a non-zero galaxy-baryon relative velocity if the equivalence principle does not hold between baryons and dark matter. We show that the relative velocity can be constrained to be less than 28% of the galaxy velocity using the cross-power spectrum of the HI intensity mapping/H$\alpha$ galaxy survey and the bispectrum of the H$\alpha$ galaxy survey.