A Universal Bound on Excitations of Heavy Fields during Inflation
arXiv:1405.7969 · doi:10.1088/1475-7516/2014/09/029
Abstract
We discuss a universal bound on any excitation of heavy fields during inflation: the ratio of the heavy field's energy density to the one driving inflation must be less than the maximally allowed relative amplitude of oscillations in the power-spectrum (less than one percent according to PLANCK). This bound can be traced back to the sudden change of the equation of state parameter across the excitation event. We employ a sudden transition approximation at the perturbed level, which has been used before in different settings; we check its validity by comparison to the full multi-field result in a concrete case study involving a sudden mass change of an inflaton.
31 pages, 9 figures; v2: reference added, minor typos corrected, conclusions unchanged
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