Sensibilità di LHAASO alla Violazione della Lorentz-Invariance durante episodi di flare negli AGN Sensitivity of LHAASO to Lorentz Invariance Violation during AGN flares

Active Galactic Nuclei are far away extragalactic sources with the potential of being accurate probes of the space-time structure. Their emission is not constant in time, as they undergo sudden increases in flux called flares. Variability in the time pattern between higher and lower energy components during flares could be used to measure, if any, a delay between the two components which could be the first hint that the “vacuum’ is a dispersive medium, contradicting the Lorentz invariance (LIV: Lorentz-Invariance Violation), but also providing clues for unification theory. Flares have been routinely detected by Cherenkov experiments since many years and delays between high and low energy components have been measured since the first such event measured by MAGIC in 2007. That flare lasted 20 minutes and had a fast rise time of about 1 minute. During the flare the time evolution of higher energy gamma rays (1.2 TeV) was delayed by 4 minutes with respect to the lower energy one at 0.25 TeV. Whereas the delay could be ascribed entirely to astrophysical causes (like that the flaring activity itself is delaying higher energies emissions), more data can be used to support or disproof LIV, as if LIV is real we should expect an effect increasing with distance. It must be said that the effect on LIV is expected to be linear (or quadratic) with energy, so that it will be much more easily detected at higher energies, such as the ones in the domain of LHAASO, the new detector operating in Sichuan that is sensitive to the TeV-PeV energy range. We expect to review the current mechanisms of LIV and compare them with the current sensitivity of LHAASO.