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

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 nonsingular cyclic evolution and a hysteresislike phenomenon. 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 hysteresislike 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.

Automated summary

The problematic feature of low-energy-scale inflationary models in a spatially closed universe has been shown to be successfully resolved by considering dissipative particle production, leading to quicker onset of inflation even for highly unfavorable initial conditions. This study explores the role of dissipative effects in warm inflation scenarios and finds that entropy production sourced by such effects makes the hysteresislike phenomena stronger, allowing for a larger phase space of favorable initial conditions compared to cold inflation models.