Inflationary reheating is almost completely controlled by the Floquet indices, $mu_k$. Using spectral theory we demonstrate that the stability bands (where $mu_k = 0$) of the Mathieu and Lame equations are destroyed even in Minkowski spacetime, leaving a fractal Cantor set or a measure zero set of stable modes in the cases where the inflaton evolves in an almost-periodic or stochastic manner respectively. These two types of potential model the expected multi-field and quantum backreaction effects during reheating.
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