Weakly model-independent determination of total expansion during inflation
Abstract
We study systematically the total expansion experienced by a certain perturbation mode during single-field inflation, not resorting to explicit models of inflation or reheating. By assuming that during the reheating stage the equation of state wrh can be written as a function of e-folds, the unknown dynamics during reheating parametrized by wrh is confined within a time integral so that any dependence on the models of inflation and reheating is isolated from model-independent contributions. Especially, the dependence on the reheating dynamics via wrh and the reheating temperature Trh is dominating. We give two illustrative examples of wrh to discuss its impacts on the total expansion, which can be different as much as 10 even for the same reheating temperature, depending on the shape of wrh. We also discuss the profile degeneracy of wrh, and argue when the degeneracy is lifted.
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