Eur. Phys. J. C (2017) 77: 287
https://doi.org/10.1140/epjc/s10052-017-4840-7

Regular Article - Theoretical Physics

Cosmology with bulk viscosity and the gravitino problem

Consequences of imperfect fluids on gravitino production

¹ Dipartimento di Fisica “E.R. Caianiello” Universitá di Salerno, 84084, Fisciano, SA, Italy
² INFN-Gruppo Collegato di Salerno, Dipartimento di Fisica “E.R. Caianiello” Universitá di Salerno, 84084, Fisciano, SA, Italy

^* e-mail: lambiase@sa.infn.it

Received: 6 October 2016
Accepted: 18 April 2017
Published online: 5 May 2017

Abstract

The gravitino problem is revisited in the framework of cosmological models in which the primordial cosmic matter is described by a relativistic imperfect fluid. Dissipative effects (or bulk viscosity effects) arise owing to the different cooling rates of the fluid components. We show that the effects of the bulk viscosity allow one to avoid the late abundance of gravitinos. In particular, for particular values of the parameters characterizing the cosmological model, the gravitino abundance turns out to be weakly depending on the reheating temperature.