Emergence of Fluctuations from a Tachyonic Big Bang

TL;DR

This paper explores how cosmological fluctuations emerge from a tachyonic big bang, suggesting they form in a thermal state and discussing implications for inflationary cosmology's trans-Planckian problem.

Contribution

It introduces a model where fluctuations originate from a tachyonic big bang, contrasting with standard vacuum initial conditions.

Findings

Fluctuations emerge in a thermal state.

Comparison with vacuum initial conditions shows differences.

Discusses implications for the trans-Planckian problem.

Abstract

It has recently been speculated that the end state of a collapsing universe is a tachyonic big crunch. The time reversal of this process would be the emergence of an expanding universe from a tachyonic big bang. In this framework, we study the emergence of cosmological fluctuations. In particular, we compare the amplitude of the perturbations at tne end of the tachyon phase with what would be obtained assuming the usual vacuum initial conditions. We find that cosmological fluctuations emerge in a thermal state. We comment on the relation to the trans-Planckian problem of inflationary cosmology.