Accelerating Cosmologies from Exponential Potentials

TL;DR

This paper investigates how exponential potentials from higher-dimensional theories can lead to accelerated expansion in four-dimensional cosmologies, highlighting conditions for eternal acceleration and effects of spatial curvature.

Contribution

It provides analytic and numerical solutions for cosmologies with exponential potentials from hyperbolic-flux compactification, revealing conditions for eternal acceleration in M-theory inspired models.

Findings

Eternal acceleration possible with negative spatial curvature.

Transient acceleration in flat universe scenarios.

Constraints on internal space size and Kaluza-Klein modes.

Abstract

An exponential potential of the form $V\sim \exp(-2c \phi/M_p)$ arising from the hyperbolic or flux compactification of higher-dimensional theories is of interest for getting short periods of accelerated cosmological expansions. Using a similar potential but derived for the combined case of hyperbolic-flux compactification, we study the four-dimensional flat (and open) FLRW cosmologies and give analytic (and numerical) solutions with exponential behavior of scale factors. We show that, for the M-theory motivated potentials, the cosmic acceleration of the universe can be eternal if the spatial curvature of the 4d spacetime is negative, while the acceleration is only transient for a spatially flat universe. We also comment on the size of the internal space and its associated geometric bounds on massive Kaluza-Klein excitations.