Bounding the photon mass with cosmological propagation of fast radio bursts

TL;DR

This paper uses cosmological observations of fast radio bursts to set the most stringent limit yet on the photon mass, constraining it to be less than approximately 1.7 x 10^{-15} eV/c^2 with 68% confidence.

Contribution

It introduces a novel Bayesian analysis of 129 FRBs to improve constraints on the photon mass using cosmological propagation data.

Findings

Photon mass constrained to ≤ 1.7 x 10^{-15} eV/c^2 at 68% confidence

Achieved the best limit from light propagation kinematics to date

Future data will further tighten the photon mass bounds

Abstract

Photon is the fundamental quantum of electromagnetic fields, whose mass, $m_{\gamma}$, should be strictly zero in Maxwell's theory. But not all theories adopt this hypothesis. If the rest mass of the photon is not zero, there will be an additional time delay between photons of different frequencies after they travel through a fixed distance. By analyzing the time delay, we can measure or constrain the photon mass. Fast radio bursts (FRBs) -- transient radio bursts characterized by millisecond duration and cosmological propagation -- are excellent astrophysical laboratories to constrain $m_{\gamma}$. In this work we use a catalog of 129 FRBs in a Bayesian framework to constrain $m_{\gamma}$. As a result, we obtain a new bound on the photon mass, $m_{\gamma} \leq 3.1\times 10^{-51}\rm\,kg\simeq 1.7 \times 10^{-15}\,eV/c^2$ ($m_{\gamma} \leq 3.9\times 10^{-51}\rm\,kg \simeq 2.2 \times 10^{-15}\,eV/c^2$) at the $68\%$ $(95\%$) confidence level. The result represents the best limit purely from kinematic analysis of light propagation. The bound on the photon mass will be tighter in the near future with increment in the number of FRBs, more accurate measurement of the redshift for FRBs, and refinement in the knowledge about the origin of dispersion measures (DMs).