Quintessence as a run-away dilaton

TL;DR

This paper explores a cosmological model where a runaway dilaton from string theory acts as quintessence, driving the Universe's late-time accelerated expansion with potential deviations from General Relativity in dark matter.

Contribution

It proposes a novel late-time cosmological scenario based on the infinite-bare-coupling limit of string theory, linking the dilaton's behavior to dark energy and modified gravity effects.

Findings

Dilaton can serve as quintessence field causing accelerated expansion.

Universe transitions from focusing to dragging regime over cosmic history.

Possible observable deviations from General Relativity in dark matter sector.

Abstract

We consider a late-time cosmological model based on a recent proposal that the infinite-bare-coupling limit of superstring/M-theory exists and has good phenomenological properties, including a vanishing cosmological constant, and a massless, decoupled dilaton. As it runs away to $+ \infty$, the dilaton can play the role of the quintessence field recently advocated to drive the late-time accelerated expansion of the Universe. If, as suggested by some string theory examples, appreciable deviations from General Relativity persist even today in the dark matter sector, the Universe may smoothly evolve from an initial "focusing" stage, lasting untill radiation--matter equality, to a "dragging" regime, which eventually gives rise to an accelerated expansion with frozen $\Omega(\rm{dark energy})/\Omega(\rm{dark matter})$.