Unnatural Oscillon Lifetimes in an Expanding Background

TL;DR

This paper studies how oscillons, localized scalar field configurations, can have extremely long lifetimes in an expanding universe, with lifetimes exponentially increasing with their energy, despite decay mechanisms.

Contribution

It introduces a simple 1+1D scalar field model demonstrating that oscillons can have exponentially large lifetimes in an expanding background, highlighting a new decay suppression mechanism.

Findings

Oscillon lifetimes scale exponentially with energy in an expanding universe.

Lifetimes depend on the expansion rate, with specific scaling constants.

Oscillons can persist for durations much longer than naive expectations in cosmological settings.

Abstract

We consider a classical toy model of a massive scalar field in 1+1 dimensions with a constant exponential expansion rate of space. The nonlinear theory under consideration supports approximate oscillon solutions, but they eventually decay due to their coupling to the expanding background. Although all the parameters of the theory and the oscillon energies are of order one in units of the scalar field mass $m$, the oscillon lifetime is exponentially large in these natural units. For typical values of the parameters, we see oscillon lifetimes scaling approximately as $\tau \propto \exp(k E/m)/m$ where $E$ is the oscillon energy and the constant $k$ is on the order of 5 to 15 for expansion rates between $H=0.02m$ and $H=0.01m$.