Particle production in an expanding universe dominated by dark energy fluid

Abstract

We investigate particle production in an expanding universe dominated by a perfect fluid with the equation of state p = αρ. The rate of particle production, using the Bogoliubov coefficients, is determined exactly for any value of α 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.