Thoughts on Tachyon Cosmology

TL;DR

This paper reviews challenges in achieving inflation within M/String Theory, discusses the potential role of tachyons in cosmology, and explores the possibility of tachyons influencing a pre-inflationary era.

Contribution

It provides a pedagogical overview of cosmological obstacles in string theory and introduces recent ideas about tachyons' roles in early universe scenarios.

Findings

Revisits the No-Go Theorem for inflation in string theory

Highlights objections to naive tachyon inflation models

Proposes tachyons may have influenced a pre-inflationary era

Abstract

After a pedagogical review of elementary cosmology, I go on to discuss some obstacles to obtaining inflationary or accelerating universes in M/String Theory. In particular, I give an account of an old No-Go Theorem to this effect. I then describe some recent ideas about the possible r\^ole of the tachyon in cosmology. I stress that there are many objections to a naive inflationary model based on the tachyon, but there remains the possiblity that the tachyon was important in a possible pre-inflationary Open-String Era preceding our present Closed String Era.