Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

TL;DR

This paper investigates transitions from accelerated to decelerated expansion in 2D cosmological models using JT and CGHS frameworks, incorporating van der Waals equations to simulate inflation and subsequent deceleration.

Contribution

It introduces a novel approach using van der Waals equations in 2D models to simulate inflation and transition to deceleration, analyzing JT and CGHS models' dynamical behavior.

Findings

Successful simulation of inflation followed by negative acceleration.

Transition from inflation to deceleration depends on initial conditions.

Physical quantities like scale factor and energy density evolve consistently.

Abstract

In this work we discuss the possibility of positive-acceleration regimes, and their transition to decelerated regimes, in two-dimensional (2D) cosmological models. We use general relativity and the thermodynamics in a 2D space-time, where the gas is seen as the sources of the gravitational field. An early-Universe model is analyzed where the state equation of van der Waals is used, replacing the usual barotropic equation. We show that this substitution permits the simulation of a period of inflation, followed by a negative-acceleration era. The dynamical behavior of the system follows from the solution of the Jackiw-Teitelboim equations (JT equations) and the energy-momentum conservation laws. In a second stage we focus the Callan-Giddings-Harvey-Strominger model (CGHS model); here the transition from the inflationary period to the decelerated period is also present between the solutions, although this result depend strongly on the initial conditions used for the dilaton field. The temporal evolution of the cosmic scale function, its acceleration, the energy density and the hydrostatic pressure are the physical quantities obtained in through the analysis.