Topological Defects as Seeds for Eternal Inflation

TL;DR

The paper investigates how the global structure of the inflationary universe depends on the inflationary mechanism, comparing chaotic inflation with models where inflation occurs near a local maximum of $V(\phi)$ and in symmetry-related extrema. Using analytical methods and stochastic simulations, it shows that inflating domain walls, strings, and monopoles can undergo self-reproduction, producing fractal, self-similar networks that seeds eternal inflation. Key findings include that inflating defects persist and proliferate, potentially surrounding islands of thermalized phase and even forming fractal defect interiors that drive further inflation. This work reveals a robust link between topological defects and eternal inflation, offering new perspectives on initial conditions and the large-scale structure of the cosmos.

Abstract

We investigate the global structure of inflationary universe both by analytical methods and by computer simulations of stochastic processes in the early Universe. We show that the global structure of the universe depends crucially on the mechanism of inflation. In the simplest models of chaotic inflation the Universe looks like a sea of thermalized phase surrounding permanently self-reproducing inflationary domains. In the theories where inflation occurs near a local extremum of the effective potential corresponding to a metastable state, the Universe looks like de Sitter space surrounding islands of thermalized phase. A similar picture appears even if the state $φ= 0$ is unstable but the effective potential has a discrete symmetry $φ\to =-φ$. In this case the Universe becomes divided into domains containing different phases. These domains will be separated from each other by domain walls. However, unlike ordinary domain walls, these domain walls will inflate, and their thickness will exponentially grow. In the theories with continuous symmetries inflation generates exponentially expanding strings and monopoles surrounded by thermalized phase. Inflating topological defects will be stable, and they will unceasingly produce new inflating topological defects. This means that topological defects may play a role of indestructible seeds for eternal inflation.