The Hagedorn transition in non-commutative open string theory

TL;DR

This paper studies the Hagedorn transition in non-commutative open string theories, revealing a second-order transition in up to five dimensions and discussing the nature of the high-temperature phase involving long strings.

Contribution

It provides a detailed analysis of the Hagedorn transition in NCOS theories, especially in dimensions up to five, highlighting the role of long strings and the effects of interactions.

Findings

Hagedorn transition is second order in ≤5 dimensions.

High temperature phase involves long, nearly straight strings.

Interaction effects become significant above five dimensions.

Abstract

The Hagedorn transition in non-commutative open string theory (NCOS) is relatively simple because gravity decouples. For NCOS theories in no more than five spacetime dimensions, the Hagedorn transition is second order, and the high temperature phase involves long, nearly straight fundamental strings separating from the D-brane on which the NCOS theory is defined. Above five spacetime dimensions interaction effects become important below the Hagedorn temperature. Although this complicates studies of the transition, we believe that the high temperature phase again involves long strings liberated from the bound state.