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

Abstract

We explore the warm inflation scenario theoretical predictions looking at two different dissipative regimes for several representative primordial potentials. As it is well known, the warm inflation is able to decrease the tensor-to-scalar ratio value, rehabilitating several primordial potential ruled out in the cold inflation context by the recent cosmic microwave background data. Here we show that it is also able to produce a running of the running n s positive and within the Planck data limits. This is very remarkable since the standard cold inflation model is unable to justify the current indication of a positive constraint on n s . We achieve a parameterization for the primordial power spectrum able to take into account higher order effects as the running of the spectral index and the running of the running, and we perform statistical analysis using the most up-to-date Planck data to constrain the dissipative effects. We find that the warm inflation can explain the current observables with a good statistical significance, even for those potentials ruled out in the simplest cold inflation scenario.

Predictions of Spectral Parameters by Several Inflationary Universe Models in Light of the Planck Results

“…From the Planck-data he found β S 0.025 ± 0.013. This is in good agreement with the analysis of Benetti and Ramos [44], giving β s 0.029 ± 0.015. Inserting (4.4) and (4.13) into Equation (4.29) gives ξ in terms of observable quantities,…”

“…In October 2016 Benetti and Ramos [44] gave α s = 0.011 ± 0.014 while Ballesteros and Casas [31] gave a smaller uncertainty, α S = − 0.018 ± 0.009, excluding values very close to zero. In January 2016 Bamba et al [45] gave, n S = 0.968 ± 0.006, r < 0.11, α S = − 0.003 ± 0.007.…”

“…However the BICEP/Planck data alone constrain the tensor tilt to n T = 0.66 44 , so the actual value of n T is presently quite uncertain. However if it turns out that future observations imply a large absolute value of n T , say |n T | > 2, then most present inflationary models are in trouble.…”

Adiabatic out-of-equilibrium solutions to the Boltzmann equation in warm inflation

“…In particular, for weak dissipation at horizon-crossing, predictions for n s and r differ significantly for the limiting cases where inflaton fluctuations are in a vacuum or in a thermal state (i.e., in equilibrium with the overall thermal bath) [17,19]. Although for strong dissipation this issue becomes less relevant, since dissipation becomes the dominant source of inflaton fluctuations, agreement with observations in most scenarios considered so far typically favours the Q * 1 regime [17,19,[48][49][50]. The dissipative dynamics itself is not sufficient to determine the state of inflaton fluctuations, since other processes in the thermal bath can be responsible for a substantial creation and annihilation of inflaton particles.…”

Warm brane inflation with an exponential potential: A consistent realization away from the swampland

“…As a matter of fact, the primordial power spectrum for WI at horizon crossing can be expressed in the form (see, e.g., Ref. [47] and references therein)…”