Hartle-Hawking Vacuum for c=1 Tachyon Condensation

TL;DR

This paper constructs quantum vacua for a time-symmetric cosmology involving closed string tachyon condensation in 2D string theory, revealing thermal states with properties similar to the Hartle-Hawking vacuum.

Contribution

It introduces a method to construct quantum vacua in a time-dependent setting with Euclidean periodicity, leading to thermal states at discrete temperatures in 2D string theory.

Findings

Asymptotic thermal Green functions are computed.

Stress energy tensor exhibits properties similar to Hartle-Hawking vacuum.

Thermal states exist at discrete temperature values.

Abstract

Quantum vacua are constructed for a time-symmetric cosmology describing closed string tachyon condensation in two-dimensional string theory. Due to the Euclidean periodicity of the solution, and despite its time dependence, we are able to construct thermal states at discrete values of the temperature. The asymptotic thermal Green functions and stress energy tensor are computed and found to have an intriguing resemblance to those in the Hartle-Hawking vacuum of a black hole.