2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/193976We consider a cosmological horizon, named thermo-horizon, to which are associated a temperature and an entropy of Bekenstein-Hawking and which obeys the first law for an energy flow calculated through the corresponding limit surface. We point out a contradiction between the first law and the definition of the total energy contained inside the horizon. This contradiction is removed when the first law is replaced by a Gibbs' equation for a vacuum-like component associated to the event horizon.High Energy Physics - TheoryAstrophysicsGeneral Relativity and Quantum Cosmologytext