Cosmological tachyon from cubic string field theory

TL;DR

This paper explores the cosmological dynamics of tachyon fields derived from cubic string field theory, analyzing their equations of motion, stability, and relation to other models within a broad theoretical framework.

Contribution

It introduces a comprehensive analysis of tachyon cosmology from cubic string field theory, including nonlocal actions and generalized equations applicable to various gravity models.

Findings

Derived equations of motion in Hamilton-Jacobi formalism.

Analyzed slow-roll approximation validity and perturbation stability.

Established connections between tachyon and Dirac-Born-Infeld models.

Abstract

The classical dynamics of the tachyon scalar field of cubic string field theory is considered on a cosmological background. Starting from a nonlocal action with arbitrary tachyon potential, which encodes the bosonic and several supersymmetric cases, we study the equations of motion in the Hamilton-Jacobi formalism and with a generalized Friedmann equation, appliable in braneworld or modified gravity models. The cases of cubic (bosonic) and quartic (supersymmetric) tachyon potential in general relativity are automatically included. We comment the validity of the slow-roll approximation, the stability of the cosmological perturbations, and the relation between this tachyon and the Dirac-Born-Infeld one.