http://arxiv.org/abs/1509.00163
The thermal history of a large class of running vacuum models in which the effective cosmological term is a truncated power series of the Hubble rate, whose dominant term is $\Lambda (H) \propto H^{n+2}$, is discussed in detail. Specifically, the temperature evolution law and the increasing entropy function are analytically calculated. For the whole class of vacuum models explored here we find that the primeval value of the comoving radiation entropy density (associated to effectively massless particles) starts from zero and evolves extremely fast until reaching a maximum near the end of the vacuum decay phase, where it saturates in the present day value within the current Hubble radius. We find that the whole class of running vacuum models predicts the same correct value of the total entropy at present, $S_{0} \sim 10^{88}$ (in natural units), independently of the initial conditions. If, however, we impose the Gibbons-Hawking temperature as an initial condition, we find that the ratio between the primeval and late time vacuum energy densities is $\rho_{vI}/\rho_{v0} \sim 10^{123}$.
J. Lima, S. Basilakos and J. Sola
Wed, 2 Sep 15
25/87
Comments: 13 pages in free style, 2 figures. arXiv admin note: substantial text overlap with arXiv:1412.5196
You must be logged in to post a comment.