Emergence of Oscillons in an Expanding Background

TL;DR

This paper investigates how oscillons, localized oscillatory solutions in scalar fields, behave in an expanding universe, showing they lose energy slowly and can dominate the energy content under certain conditions, with potential cosmological implications.

Contribution

It demonstrates that oscillons in an expanding background lose energy at an exponentially slow rate and can store a significant fraction of the universe's energy, revealing their possible cosmological importance.

Findings

Oscillons lose energy very slowly in an expanding universe.

A universe with thermal initial conditions can end with about 50% of energy in oscillons.

Oscillons may have significant cosmological consequences if this behavior persists in realistic models.

Abstract

We consider a (1+1) dimensional scalar field theory that supports oscillons, which are localized, oscillatory, stable solutions to nonlinear equations of motion. We study this theory in an expanding background and show that oscillons now lose energy, but at a rate that is exponentially small when the expansion rate is slow. We also show numerically that a universe that starts with (almost) thermal initial conditions will cool to a final state where a significant fraction of the energy of the universe -- on the order of 50% -- is stored in oscillons. If this phenomenon persists in realistic models, oscillons may have cosmological consequences.