2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187508It is known that the kinetic mixing of photon and another U(1)_ex gauge boson can introduce millicharged particles. Millicharged particles $f$ of mass 0.1 eV can explain the PVLAS experiment. We suggest a temperature dependent gauge symmetry breaking of U(1)_ex for this idea to be consistent with astrophysical and cosmological constraints.9 pages, 3 figuesHigh Energy Physics - Phenomenologytext