On the role of dissipative effects in the quantum gravitational onset of warm Starobinsky inflation in a closed universe

Abstract

A problematic feature of low energy scale inflationary models, such as Starobinsky inflation, in a spatially closed universe is the occurrence of a recollapse and a big crunch singularity before inflation can even set in. In a recent work it was shown that this problem can be successfully resolved in loop quantum cosmology for a large class of initial conditions due to a non-singular cyclic evolution and a hysteresis-like phenomena. However, for certain highly unfavorable initial conditions the onset of inflation was still difficult to obtain. In this work, we explore the role of dissipative particle production, which is typical in warm inflation scenario, in the above setting. We find that entropy production sourced by such dissipative effects makes hysteresis-like phenomena stronger. As a result, the onset of inflation is quick in general including for highly unfavorable initial conditions where it fails or is significantly delayed in the absence of dissipative effects. We phenomenologically consider three warm inflation scenarios with distinct forms of dissipation coefficient, and from dynamical solutions and phase space portraits find that the phase space of favorable initial conditions turns out to be much larger than in cold inflation.