Power spectrum for inflation models with quantum and thermal noises

Abstract

We determine the power spectrum for inflation models covering all regimes from cold (isentropic) to warm (nonisentropic) inflation. We work in the context of the stochastic inflation approach, which can nicely describe both types of inflationary regimes concomitantly. A throughout analysis is carried out to determine the allowed parameter space for simple single field polynomial chaotic inflation models that is consistent with the most recent cosmological data from the nine-year Wilkinson Microwave Anisotropy Probe (WMAP) and in conjunction with other observational cosmological sources. We present the results for both the amplitude of the power spectrum, the spectral index and for the tensor to scalar curvature perturbation amplitude ratio. We briefly discuss cases when running is present. Despite single field polynomial-type inflaton potential models be strongly disfavored, or even be already ruled out in their simplest versions in the case of cold inflation, this is not the case for nonisentropic inflation models in general (warm inflation in particular), though higher order polynomial potentials (higher than quartic order) tend to become less favorable also in this case, presenting a much smaller region of parameter space compatible with the recent observational cosmological data. Our findings also remain valid in face of the recently released Planck results.

Warm intermediate inflationary Universe model in the presence of a generalized Chaplygin gas

“…[51][52][53][54][55][56][57]. In this form, from the definition of the parameter ε, the value of the scalar field φ 1 as a result is…”

“…The model of intermediate inflation was in the beginning formulated as an exact solution to the background equations, nevertheless, this model may be studied under the slowroll approximation together with the cosmological perturbations. In particular, under the slow-roll analysis, the effective potential is a power-law type, and the scalar spectral index becomes n s ∼ 1, and exactly n s = 1 (Harrizon-Zel'dovich spectrum) for the special value f = 2/3 [51][52][53][54][55][56][57]. In the same way, the tensor-to-scalar ratio r becomes r = 0 [58][59][60][61].…”

Constraints on just enough inflation preceded by a thermal era

“…If the inflaton fluctuations are also in thermal equilibrium with the thermal bath there will again be a coth term in the density perturbation spectrum, as seen, for example, in Refs. [29][30][31]. In both thermal and warm inflation, the presence of the coth term would affect density perturbations with large power on the relevant large scales, as in Ref.…”

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

“…[8][9][10][11]). The greatest appeal of warm inflation lies perhaps in the fact that thermal inflaton fluctuations are directly sourced by dissipative processes, changing the form of the primordial spectrum of curvature perturbations and thus providing a unique observational window into the particle physics behind inflation [11][12][13][14][15][16][17][18]. In addition, we have recently shown that warm inflation can be consistently realized in a simple quantum field theory framework requiring very few fields, the Warm Little Inflaton scenario [19], where the required flatness of the inflaton potential is not spoiled by thermal effects (see also refs.…”