Dark photon dark matter and fast radio bursts

The nature of dark matter is still a mystery that may indicate the necessity for extensions of the Standard Model (SM). The lack of positive signatures for well-known dark matter candidates, such as Weakly Interacting Massive Particles, opens new avenues of exploration. Among them, a new abelian gauge field (dark photon), which kinetically mixes with the SM hypercharge field, is a possible mediator of the interaction between a dark matter candidate and the SM particles. Light dark photons may also comprise partially or entirely the observed dark matter density and existing limits for the dark photon dark matter parameter space arise from several cosmological and astrophysical sources. In the present work we investigate dark photon dark matter using cosmic transients, specifically fast radio bursts (FRBs). The observed time delay of radio photons with different energies have been used to constrain the photon mass or the Weak Equivalence Principle (WEP), for example. Due to the mixing between the visible and the dark photon, the time delay of photons from these cosmic transients, caused by free electrons in the intergalactic medium, can change and impact those constraints from FRBs. We use five detected FRBs (FRB 110220, FRB 121102, FRB 150418, FRB180924 and FRB 190523) and two associations of FRBs with gamma-ray bursts (FRB/GRB 101011A and FRB/GRB 100704A) to investigate the correspondent variation on the time delay caused by the presence of dark photon dark matter. The result is virtually independent of the FRB used and this variation is very small to be detectable in the near future, considering the still allowed dark photon dark matter parameter space. The existing bounds on the photon mass or the WEP arising from FRBs are, therefore, not jeopardized.