CONICET | Buscador de Institutos y Recursos Humanos

Macroscopic irreversible processes emerge from fundamental physical laws of reversible character. Thesource of the local irreversibility observed, seems not to be in the laws themselves but in the initialand boundary conditions of the equations that represent the laws. In this work we propose that thescreening of electromagnetic currents by black hole event horizons in the solution of Maxwell?s equationsdetermines, locally, a preferred temporal direction for the flux of electromagnetic energy that followsthe expansion of the universe. Specifically, we calculate the growth of black hole event horizons dueto the cosmological expansion and accretion of cosmic microwave background radiation, for differentcosmological models. We find that for the flat, open, and closed Friedmann cosmological models, thequotient of the area of the black hole event horizon and the area of a comoving space-like hypersurfaceis always larger than one. This implies that for any spacetime event, its causal past and future are notsymmetric, causing then a net Poynting flux in the global future direction; the latter is in turn related tothe ever increasing thermodynamic entropy.