Limits on Einstein's Equivalence Principle from the first localized Fast Radio Burst FRB 150418

Understand

Fast Radio Bursts have recently been used to place limits on Einstein's Equivalence Principle via observations of time delays between photons of different radio frequencies by \citet{wei15}.

• These limits on differential post-Newtonian parameters ($\Delta \gamma<2.52\times10^{-8}$) are the best yet achieved but still rely on uncertain assumptions, namely the relative contributions of dispersion and gravitational delays to the observed time delays and the distances to FRBs.
• Also very recently, the first FRB host galaxy has likely been identified, providing the first redshift-based distance estimate to FRB 150418 \citep{kea16}.
• Moreover, consistency between the \omegaigm\ estimate from FRB 150418 and \omegaigm~expected from $\Lambda$CDM models and WMAP observations leads one to conclude that the observed time delay for FRB 150418 is highly dominated by dispersion, with any gravitational delays small contributors.