Eternal inflation in a dissipative and radiation environment: Heated demise of eternity

Abstract

Eternal inflation is studied in the context of warm inflation. We focus on different tools to analyze the effects of dissipation and the presence of a thermal radiation bath on the fluctuation-dominated regime, for which the self-reproduction of Hubble regions can take place. The tools we explore are the threshold inflaton field and threshold number of e-folds necessary to establish a self-reproduction regime and the counting of Hubble regions, using generalized conditions for the occurrence of a fluctuation-dominated regime. We obtain the functional dependence of these quantities on the dissipation and temperature. A Sturm-Liouville analysis of the Fokker-Planck equation for the probability of having eternal inflation and an analysis for the probability of having eternal points are performed. We have considered the representative cases of inflation models with monomial potentials of the form of chaotic and hilltop ones. Our results show that warm inflation tends to initially favor the onset of a self-reproduction regime for smaller values of the dissipation. As the dissipation increases, it becomes harder than in cold inflation (i.e., in the absence of dissipation) to achieve a self-reproduction regime for both types of models analyzed. The results are interpreted and explicit analytical expressions are given whenever that is possible.

Warm inflation dissipative effects: Predictions and constraints from the Planck data

“…[21,22]). Dissipative and stochastic processes typically involved in the WI dynamics [10,12,13,[23][24][25][26][27] are able to produce a strongly modified dynamics, both at the background and the fluctuations levels, leading to many distinguished predictions with respect to the CI scenario. In particular, in WI the primary source of density fluctuations comes from thermal fluctuations originated in the radiation bath and transported to the inflaton field as adiabatic curvature perturbations [28,29], while in CI the density perturbations are due to quantum fluctuations of the inflaton field [30].…”

Identifying universality in warm inflation

“…Recently a first principles warm inflation model was constructed from QFT which involves just a few fields [27], thus convincingly demonstrating that warm inflation models are on an equal footing to cold inflation as model building prospects. Moreover, the dissipative effects and the presence of a non-vanishing radiation bath are able to change both the inflationary dynamics at the background and at the fluctuation levels [29][30][31][32][33][34][35][36][37], such that there can be distinctive differences between the two paradigms which could be testable. As such, it is useful to understand the dynamical structure of warm inflation through different perspectives, which is a motivation of this paper.…”

Probability of warm inflation in loop quantum cosmology

“…WI has much developed in recent years such as to be able to provide insights on some outstanding problems related to the inflationary picture and which CI cannot directly answer. Some of these insights include for example the question of eternal inflation in the context of WI [11], a solution for the so called η−problem [12] that appears in supergravity or string inflation models, the role of dissipation in selecting favorable inflationary trajectories and in alleviating the fine-tuning problem of inflation [13,14] (see also Ref. [15] for a recent detailed analysis of the effect of dissipation and stochastic noise effects, typical of warm inflation dynamics, in setting initial conditions for inflation).…”