Axion-like particle effects on the polarization of cosmic high-energy gamma sources

Understand

Various satellite-borne missions are being planned whose goal is to measure the polarization of a large number of gamma-ray bursts (GRBs).

• We show that the polarization pattern predicted by current models of GRB emission can be drastically modified by the existence of very light axion-like particles (ALPs), which are present in many extensions of the Standard Model of particle physics.
• Basically, the propagation of photons emitted by a GRB through cosmic magnetic fields with a domain-like structure induces photon-ALP mixing, which is expected to produce a strong modification of the original photon polarization.
• Because of the random orientation of the magnetic field in each domain, this effect strongly depends on the orientation of the photon line of sight.