# Particle production in an expanding universe dominated by dark energy fluid

* A.B. Batista, J.C. Fabris and S.J.M. Houndjo*^{1}

(1) Departamento de Fisica, Universidade Federal do Espirito Santo, 29060-900, Vitoria, Espirito Santo, Brazil

### Abstract

We investigate particle production in an expanding universe dominated by a perfect fluid with the equation of state *p* = ar. The rate of particle production, using the Bogoliubov coefficients, is determined exactly for any value of a in the case of a flat universe. When the strong energy condition is satisfied, the particle production rate decreases with time; the opposite occurs when the strong energy condition is violated. In the phantom case, the particle production rate diverges in a finite time for each mode represented by a wavenumber *k*. Nevertheless, the energy density associated with the produced particles tends to zero as the big rip is approached.

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