Accelerated expansion in bosonic and fermionic 2D cosmologies with quantum effects

TL;DR

This paper investigates how quantum effects and matter types influence accelerated expansion in 2D cosmological models, revealing that fermionic matter can lead to a transition from acceleration to deceleration.

Contribution

It introduces a 2D cosmological model incorporating quantum corrections, bosonic and fermionic matter, and the dilaton field, demonstrating novel effects on cosmic expansion behaviors.

Findings

Quantum effects significantly influence the expansion dynamics.

Fermionic matter can cause a transition from accelerated to decelerated expansion.

Bosonic matter alone maintains accelerated expansion without transition.

Abstract

In this work we analyze the effects produced by bosonic and fermionic constituents, including quantum corrections, in two-dimensional (2D) cosmological models. We focus on a gravitational theory related to the Callan-Giddings-Harvey-Strominger model, to simulate the dynamics of a young, spatially-lineal, universe. The cosmic substratum is formed by an {\it inflaton} field plus a matter component, sources of the 2D gravitational field; the degrees of freedom also include the presence of a dilaton field. We show that this combination permits, among other scenarios, the simulation of a period of inflation, that would be followed by a (bosonic/fermionic) matter dominated era. We also analyse how quantum effects contribute to the destiny of the expansion, given the fact that in 2D we have a consistent (renormalizable) quantum theory of gravity. The dynamical behavior of the system follows from the solution of the gravitational field equations, the (Klein-Gordon and Dirac) equations for the sources and the dilaton field equation. Consistent (accelerated) regimes are present among the solutions of the 2D equations; the results depend strongly on the initial conditions used for the dilaton field. In the particular case where fermions are included as matter fields a transition to a decelerated expansion is possible, something that does not happen in the exclusively bosonic case.