Heterotic Strings in Two Dimensions and New Stringy Phase Transitions

TL;DR

This paper explores two-dimensional heterotic string theories with specific gauge groups, revealing new phase transitions and unusual thermodynamic behavior at certain compactification points.

Contribution

It introduces the analysis of heterotic strings in two dimensions with detailed spectrum and phase transition phenomena, including novel behaviors in thermal theories.

Findings

Identification of massless string states at special points

Discovery of first order phase transitions in compactified theories

Unusual thermodynamic behavior above phase transition points

Abstract

We discuss heterotic string theories in two dimensions with gauge groups Spin(24) and Spin(8) x E_8. After compactification the theories exhibit a rich spectrum of states with both winding and momentum. At special points some of these stringy states become massless, leading to new first order phase transitions. For example, the thermal theories exhibit standard thermodynamics below the phase transition, but novel and peculiar behavior above it. In particular, when the radius of the Euclidean circle is smaller than the phase transition point the torus partition function is not given by the thermal trace over the spacetime Hilbert space. The full moduli space of compactified theories is 13 dimensional, when Wilson lines are included; the Spin(24) and Spin(8) x E_8 theories correspond to distinct decompactification limits.