Warming up for Planck

TL;DR

This paper explores how warm inflation models, involving thermal effects and dissipative processes, can be tested against Planck data, offering new relations between cosmological observables and implications for baryon asymmetry.

Contribution

It derives testable relations between CMB observables in warm inflation, especially in supersymmetric models, and examines their consistency with Planck data, including baryon asymmetry generation.

Findings

Thermal bath during inflation reduces tensor-to-scalar ratio.

Derived new consistency relations for scalar and tensor modes.

Baryon asymmetry can be generated during inflation with observable isocurvature modes.

Abstract

The recent Planck results and future releases on the horizon present a key opportunity to address a fundamental question in inflationary cosmology of whether primordial density perturbations have a quantum or thermal origin, i.e. whether particle production may have significant effects during inflation. Warm inflation provides a natural arena to address this issue, with interactions between the scalar inflaton and other degrees of freedom leading to dissipative entropy production and associated thermal fluctuations. In this context, we present relations between CMB observables that can be directly tested against observational data. In particular, we show that the presence of a thermal bath warmer than the Hubble scale during inflation decreases the tensor-to-scalar ratio with respect to the conventional prediction in supercooled inflation, yielding $r< 8|n_t|$, where $n_t$ is the tensor spectral index. Focusing on supersymmetric models at low temperatures, we determine consistency relations between the observables characterizing the spectrum of adiabatic scalar and tensor modes, both for generic potentials and particular canonical examples, and which we compare with the WMAP and Planck results. Finally, we include the possibility of producing the observed baryon asymmetry during inflation through dissipative effects, thereby generating baryon isocurvature modes that can be easily accommodated by the Planck data.