Tachyon-Dilaton-induced Inflation as an alpha'-resummed String Background

TL;DR

This paper explores a novel string-theoretic inflation model involving tachyon, dilaton, and graviton backgrounds, ensuring conformal invariance and viable cosmological evolution compatible with perturbative string theory.

Contribution

It introduces a resummed inflationary scenario in string theory with a focus on Weyl anomaly cancellation and conformal invariance through background field relations.

Findings

Inflationary solutions can lead to de Sitter or smooth interpolating universes.

The model maintains conformal invariance to all orders in the Regge slope.

Compatible with perturbative string scattering amplitudes.

Abstract

Within the framework of a novel functional method on the world-sheet of the string, we discuss simple but re-summed (in the Regge slope) inflationary scenarios in the context of closed Bosonic strings, living in four target-space dimensions, in the presence of non-trivial tachyon, dilaton and graviton cosmological backgrounds. The inflationary solutions are argued to guarantee the vanishing of the corresponding Weyl anomaly coefficients in a given world-sheet renormalization scheme, thereby ensuring conformal invariance of the corresponding sigma-model to all orders in the Regge slope. The key property is the requirement of "homogeneity" of the corresponding Weyl anomaly coefficients. Inflation entails appropriate relations between the dilaton and tachyon field configurations, whose form can lead to either a de Sitter vacuum, incompatible though (due to the cosmic horizons) with the perturbative string scattering amplitudes, or to cosmic space-times involving brief inflationary periods, interpolating smoothly between power-law and/or Minkowski Universes. The latter situation is characterized by well-defined scattering amplitudes, and is thus compatible with a perturbative string framework. It is this scenario that we consider a self-consistent ground state in our framework, which is based on local field redefinitions of background fields.