Closed String Tachyon Driving $f(R)$ Cosmology

TL;DR

This paper explores how quantum effects influence closed string tachyon dynamics in $f(R)$ gravity, revealing modified classical solutions and potential bounded dilaton behavior during tachyon rolling.

Contribution

It introduces an $f(R)$ framework to incorporate quantum corrections into tachyon-driven cosmology, providing new classical solutions and insights into singularity modifications.

Findings

String metric does not need to remain fixed in some solutions.

Quantum effects can modify classical singular behaviors.

Tachyon can roll down while the dilaton remains bounded.

Abstract

To study quantum effects on the bulk tachyon dynamics, we replace $R$ with $f(R)$ in the low-energy effective action that couples gravity, the dilaton, and the bulk closed string tachyon of bosonic closed string theory and study properties of their classical solutions. The $\alpha^{\prime}$ corrections of the graviton-dilaton-tachyon system are implemented in the $f(R)$. We obtain the tachyon-induced rolling solutions and show that the string metric does not need to remain fixed in some cases. The singular behavior of more classical solutions are investigated and found to be modified by quantum effects. In particular, there could exist some classical solutions, in which the tachyon field rolls down from a maximum of the tachyon potential while the dilaton expectation value is always bounded from above during the rolling process.