Dilaton, Screening of the Cosmological Constant and IR-Driven Inflation

TL;DR

This paper explores how IR quantum effects in a dilaton-gravity framework can dynamically screen the cosmological constant and drive IR-based inflation without a slow roll potential, avoiding the eta problem.

Contribution

It introduces a model where IR quantum effects cause dilaton vev shifts, leading to screening of the cosmological constant and IR-driven inflation independent of slow roll potentials.

Findings

IR effects cause a time-dependent dilaton vev shift.

Screening of the cosmological constant occurs dynamically.

IR effects can drive slow roll-like inflation without eta problem.

Abstract

It is known that infrared (IR) quantum fluctuations in de Sitter space could break the de Sitter symmetry and generate time dependent observable effects. In this paper, we consider a dilaton-gravity theory. We find that gravitational IR effects lead to a time dependent shift on the vev of the dilaton and results in a screening (temporal) of the cosmological constant/Hubble parameter. In the Einstein frame, the effect is exponentiated and can give rises to a much more notable amount of screening. Taking the dilaton as inflaton, we obtain an inflationary expansion of the slow roll kind. This inflation is driven by the IR quantum effects of de Sitter gravity and does not rely on the use of a slow roll potential. As a result, our model is free from the eta problem which baffles the standard slow roll inflation models.