Evolution of cosmological event horizons in anisotropic universes

TL;DR

This paper investigates how cosmological event horizons evolve in anisotropic universes with a positive cosmological constant, revealing their shape changes over time and the impact of dark energy on their evolution.

Contribution

It provides a detailed analysis of horizon shape evolution in anisotropic Kasner universes with cosmological constant, including effects of holographic dark energy.

Findings

Horizon shape becomes spherical at late times

Initial horizons are needle or pancake shaped

Horizon area increases over time respecting thermodynamics

Abstract

We study the evolution of cosmological event horizons in anisotropic Kasner universes in the presence of a positive cosmological constant by analyzing null geodesics. At later times, the asymptotic form of cosmological horizons is the same spherical surface as the de Sitter horizon. At the early times, however, it has non-spherical shape with its eccentricity decreases with time. The horizon area increases with time respecting the second law of thermodynamics. The initial shape of the cosmological horizon takes the form of a needle or pancake surface depending on the nature of the background spacetimes. We also discuss that the presence of the holographic dark energy will modify significantly the initial evolution of the anisotropic universes.