Dynamical suppression of non-adiabatic modes

TL;DR

This paper investigates how early universe dynamics, especially stiff contributions after inflation, can suppress non-adiabatic modes in the cosmic microwave background, refining constraints from WMAP data.

Contribution

It provides analytical and numerical examples showing how post-inflationary stiff dynamics suppress non-adiabatic modes in CMB anisotropies.

Findings

Stiff post-inflationary dynamics can significantly suppress entropic modes.

Suppression effects depend on the early plasma dynamics.

Results refine constraints on initial conditions from WMAP data.

Abstract

Recent analyses of the WMAP 5-year data constrain possible non-adiabatic contributions to the initial conditions of CMB anisotropies. Depending upon the early dynamics of the plasma, the amplitude of the entropic modes can experience a different suppression by the time of photon decoupling. Explicit examples of the latter observation are presented both analytically and numerically when the post-inflationary dynamics is dominated by a stiff contribution.