Dr Giorgio Galanti (INAF, Osservatorio Astronomico di Brera)
Axion-like particles (ALPs) are very light, neutral, pseudo-scalar bosons which are supposed to interact with two photons. They can give rise to very interesting astrophysical effects taking place in the very-high energy band and above (10 GeV – 1000 TeV) when an external magnetic field is present. We analyze the propagation of the photon-ALP beam generated as pure photons at the jet base of a BL Lac, we study the photon-ALP oscillations during its path up to us while crossing the BL Lac magnetic field, the intergalactic magnetic field which we describe by means of an improved model and the Milky Way magnetic field. Our results are of great importance for the new generation of gamma-ray observatories like CTA, HAWC, GAMMA-400, LHAASO and TAIGA-HiSCORE.