On the Nature of the Hagedorn Transition in NCOS Systems

TL;DR

This paper investigates the Hagedorn transition in NCOS systems across dimensions, combining canonical, microcanonical, and holographic analyses to propose a microscopic ionization picture as the dominant mechanism.

Contribution

It introduces a comprehensive phase diagram analysis of NCOS systems, supporting the ionization picture and exploring the effects of temperature-dependent barriers and regularization.

Findings

The ionization picture is supported as the correct description of the Hagedorn transition.

A phase of long open strings exists in regularized NCOS systems but vanishes in the strict limit.

Refinements include temperature-dependent barriers affecting the transition mechanism.

Abstract

We extend the study of the nature of the Hagedorn transition in NCOS systems in various dimensions. The canonical analysis results in a microscopic ionization picture of a bound state system in which the Hagedorn transition is postponed till irrelevancy. A microcanonical analysis leads to a limiting Hagedorn behaviour dominated by highly excited, long open strings. The study of the full phase diagram of the NCOS system using the AdS/CFT correspondence suggests that the microscopic ionization picture is the correct one. We discuss some refinements of the ionization mechanism for $d>2$ NCOS systems, including the formation of a temperature-dependent barrier for the process. Some possible consequences of this behaviour, including a potential puzzle for $d=5$, are discussed. Phase diagrams of a regularized form of NCOS systems are introduced and do accomodate a phase of long open strings which disappears in the strict NCOS limit.