Evolution of perturbations in a domain wall cosmology

TL;DR

This paper investigates how a universe with domain walls, modeled as a fluid with a specific equation of state, affects cosmic evolution, galaxy formation, and observable effects like the Sachs-Wolfe effect.

Contribution

It introduces a cosmological model combining dust and domain wall fluids, analyzing their impact on structure formation and cosmic microwave background observations.

Findings

Domain walls have an equation of state consistent with supernova data.

Galaxy formation remains largely unaffected by domain wall dominance.

Density contrast behavior changes significantly during the domain wall dominated era.

Abstract

A fluid of domain walls has an effective equation of state $p_w = - {2/3}\rho_w$. This equation of state is qualitativelly in agreement with the supernova type Ia observations. We exploit a cosmological model where the matter content is given by a dust fluid and a domain wall fluid. The process of formation of galaxies is essentially preserved. On the other hand, the behaviour of the density contrast in the ordinary fluid is highly altered when domain walls begin to dominate the matter content of the Universe. This domain wall phase occurs at relative recent era, and its possible consequences are discussed, specially concerning the Sachs-Wolfe effect.