Constraints on equivalence principle violation from gamma ray bursts
Abstract
Theories of gravity that obey the weak equivalence principle have the same parametrized postNewtonian parameter γ for all particles at all energies. The large Shapiro time delays of extragalactic sources allow us to put tight constraints on differences in γ between photons of different frequencies from spectral lag data, since a nonzero Δ γ would result in a frequencydependent arrival time. The majority of previous constraints have assumed that the Shapiro time delay is dominated by a few local massive objects, although this is a poor approximation for distant sources. In this work we consider the cosmological context of these sources by developing a sourcebysource, Monte Carlobased forward model for the Shapiro time delays by combining constrained realizations of the local density field using the Bayesian origin reconstruction from galaxies algorithm with unconstrained largescale modes. Propagating uncertainties in the density field reconstruction and marginalizing over an empirical model describing other contributions to the time delay, we use spectral lag data of gamma ray bursts from the BATSE satellite to constrain Δ γ <2.1 ×10^{15} at 1 σ confidence between photon energies of 25 keV and 325 keV.
 Publication:

Physical Review D
 Pub Date:
 October 2021
 DOI:
 10.1103/PhysRevD.104.084025
 arXiv:
 arXiv:2106.15290
 Bibcode:
 2021PhRvD.104h4025B
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 14 pages, 7 figures, 3 tables, accepted for publication in Physical Review D