Shear viscous effects on the primordial power spectrum from warm inflation

By M. Bastero-Gil, A. Berera, Rudnei O. Ramos. 2011

154 citations recorded by the source corpus.

We compute the primordial curvature spectrum generated during warm inflation, including shear viscous effects. The primordial spectrum is dominated by the thermal fluctuations of the radiation bath, sourced by the dissipative term of the inflaton field. The dissipative coefficient \Upsilon, computed from first principles in the close-to-equilibrium approximation, depends in general on the temperature T, and this dependence renders the system of the linear fluctuations coupled. Whenever the dissipative coefficient is larger than the Hubble expansion rate H, there is a growing mode in the fluctuations before horizon crossing. However, dissipation intrinsically means departures from equilibrium, and therefore the presence of a shear viscous pressure in the radiation fluid. This in turn acts as an extra friction term for the radiation fluctuations that tends to damp the growth of the perturbations. Independently of the T functional dependence of the dissipation and the shear viscosity, we find that when the shear viscous coefficient \zeta_s is larger than 3 \rho_r/H at horizon crossing, \rho_r being the radiation energy density, the shear damping effect wins and there is no growing mode in the spectrum.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/9300f9dd806b2d81f3a018801b49d45a5ebfb6dc

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In Astronomy and Astrophysics

Citations in the corpus

Power spectrum for inflation models with quantum and thermal noises (2013, background): “[16], it was found that intrinsic microscopic decay processes in the radiation bath itself can cause it to slight depart from equilibrium, giving rise to viscous dissipative effects in the radiation fluid itself.”
Dissipation coefficients from scalar and fermion quantum field interactions (2010, background): “[35, 36], where it was shown how the temperature dependence of the dissipation coefficient can affect the power spectrum of perturbations.”