Consistent Constraints on the Equivalence Principle from localised Fast Radio Bursts

Abstract

Fast Radio Bursts (FRBs) are short astrophysical transients of extragalactic origin. Their burst signal is dispersed by the free electrons in the large-scale-structure (LSS), leading to delayed arrival times at different frequencies. Another potential source of time delay is the well known Shapiro delay, which measures the space-space and time-time metric perturbations along the line-of-sight. If photons of different frequencies follow different trajectories, i.e. if the universality of free fall guaranteed by the weak equivalence principle (WEP) is violated, they would experience an additional relative delay. This quantity, however, is not an observable on the background level as it is not gauge independent, which has led to confusion in previous papers. Instead, an imprint can be seen in the correlation between the time delays of different pulses. In this paper, we derive robust and consistent constraints from twelve localised FRBs on the violation of the WEP in the energy range between 4.6 and 6 meV. In contrast to a number of previous studies, we consider our signal to be not in the model, but in the covariance matrix of the likelihood. To do so, we calculate the covariance of the time delays induced by the free electrons in the LSS, the WEP breaking terms, the Milky Way and host galaxy. By marginalising over both host galaxy contribution and the contribution from the free electrons, we find that the parametrised post-Newtonian parameter $\gamma$ characterising the WEP violation must be constant in this energy range to 1 in $10^{13}$ at 68$\%$ confidence. These are the tightest constraints to-date on $\Delta \gamma$ in this low energy range.

8 pages, 4 figures, accepted by MNRAS, matches final submitted

References in corpus (9)

• The Confrontation between General Relativity and Experiment
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• The direct localization of a fast radio burst and its host
• A census of baryons in the Universe from localized fast radio bursts
• A single fast radio burst localized to a massive galaxy at cosmological distance
• A fast radio burst localised to a massive galaxy
• Probing Galactic Halos with Fast Radio Bursts
• A measurement of Hubble's Constant using Fast Radio Bursts
• Constraints on Equivalence Principle Violation from Gamma Ray Bursts

Cited by in corpus (7)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Cosmology with fast radio bursts in the era of SKA
• Catalog-based pseudo-$C_{\ell }$s
• Fast Radio Bursts as probes of the late-time universe: a new insight on the Hubble tension
• A search for the fine-structure constant evolution from fast radio bursts and type Ia supernovae data
• Forecasting constraints on the baryon mass fraction in the IGM from fast radio bursts and type Ia supernovae
• Constraining Fundamental Constants with Fast Radio Bursts: Unveiling the Role of Energy Scale