Warm inflation model building

TL;DR

This paper reviews warm inflation models, emphasizing their dynamics, predictions, and embedding into supersymmetry, highlighting how dissipation alters inflationary parameters and can reconcile models with observational data.

Contribution

It provides a comprehensive analysis of warm inflation, including model building, supersymmetric embedding, and implications for inflationary predictions and compatibility with observations.

Findings

Dissipative dynamics allow inflation at smaller field values.

Strong dissipation regime enables sub-Planckian inflaton values.

Dissipation can make quartic models consistent with CMB data.

Abstract

We review the main aspects of the warm inflation scenario, focusing on the inflationary dynamics and the predictions related to the primordial spectrum of perturbations, to be compared with the recent cosmological observations. We study in detail three different classes of inflationary models, chaotic, hybrid models and hilltop models, and discuss their embedding into supersymmetric models and the consequences for model building of the warm inflationary dynamics based on first principles calculations. Due to the extra friction term introduced in the inflaton background evolution generated by the dissipative dynamics, inflation can take place generically for smaller values of the field, and larger values of couplings and masses. When the dissipative dynamics dominates over the expansion, in the so-called strong dissipative regime, inflation proceeds with sub-planckian inflaton values. Models can be naturally embedded into a supergravity framework, with sugra corrections suppressed by the Planck mass now under control, for a larger class of K\"ahler potentials. In particular, this provides a simpler solution to the "eta" problem in supersymmetric hybrid inflation, without restricting the K\"ahler potentials compatible with inflation. For chaotic models dissipation leads to a smaller prediction for the tensor-to-scalar ratio and a less tilted spectrum when compared to the cold inflation scenario. We find in particular that a small component of dissipation renders the quartic model now consistent with the current CMB data.