Oscillons after inflation
Amin, Mustafa (MIT)

Oscillons are massive, long-lived, localized excitations of a scalar field. We show that in a class of well-motivated models, inflation is followed by copious oscillon generation and a lengthy period of oscillon domination. In these models the full inflaton has a quadratic minimum at the origin and is shallower than quadratic away from from minimum: this set includes both monodromy models and a large class of supergravity inspired scenarios, and matches the current central values of the concordance cosmology. We assume that the inflaton is weakly coupled to other fields, so as not to quickly drain energy from the oscillons or prevent them from forming. An oscillon dominated phase is effectively matter dominated which aids gravitational growth of perturbations. Given the large subhorizon perturbations generated during resonance as well as subsequent gravitational and non-gravitational interactions between oscillons, structure formation can proceed efficiently in this phase, potentially forming primordial blackholes. In addition, like any long matter dominated phase, this phase would modify the observed spectrum of fluctuations compared to that obtained by prompt radiation domination at the end of inflation.