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Physics Letters B 650 (2007) 6571 www.elsevier.com/locate/physletb

Summary: Physics Letters B 650 (2007) 6571
Particle creation and warm inflation
Gert Aarts a,
, Anders Tranberg b
a Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom
b DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
Received 24 January 2007; received in revised form 17 April 2007; accepted 24 April 2007
Available online 5 May 2007
Editor: T. Yanagida
During cosmological inflation, it has been suggested that fields coupled to the inflaton can be excited by the slow-rolling inflaton into a quasi-
stable non-vacuum state. Within this scenario of "warm inflation", this could allow for a smooth transition to a radiation dominated Universe
without a separate reheating stage and a modification of the slow roll evolution, as the heat-bath backreacts on the inflaton through friction. In
order to study this from first principles, we investigate the dynamics of a scalar field coupled to the inflaton and N light scalar boson fields, using
the 2PI-1/N expansion for nonequilibrium quantum fields. As a first step we restrict ourselves to Minkowski spacetime, interpret the inflaton as
a time-dependent background, and use vacuum initial conditions. We find that the dominant effect is particle creation at late stages of the evolution
due to the effective time-dependent mass. The further transfer of energy to the light degrees of freedom and subsequent equilibration only occurs
after the end of inflation. As a consequence, the adiabatic constraint, which is assumed in most studies of warm inflation, is not satisfied when
starting from an initial vacuum state.


Source: Aarts, Gert - Department of Physics, University of Wales Swansea


Collections: Physics