Cosmological Models in Two Spacetime Dimensions

TL;DR

This paper explores various cosmological models in two-dimensional spacetime, analyzing phenomena like big bang, big crunch, horizons, inflation, and singularities without relying on specific equations of state.

Contribution

It provides a comprehensive analysis of (1+1)-dimensional cosmological models, revealing conditions for key phenomena and singularities without assuming particular matter properties.

Findings

Hot big bang and crunch can occur in some models

Particle horizons do not form in matter and radiation models

Physical singularities can occur in both untilted and tilted models

Abstract

Various physical properties of cosmological models in (1+1) dimensions are investigated. We demonstrate how a hot big bang and a hot big crunch can arise in some models. In particular, we examine why particle horizons do not occur in matter and radiation models. We also discuss under what circumstances exponential inflation and matter/radiation decoupling can happen. Finally, without assuming any particular equation of state, we show that physical singularities can occur in both untilted and tilted universe models if certain assumptions are satisfied, similar to the (3+1)-dimensional cases.