Dilute D-Instantons at Finite Temperature

TL;DR

This paper analyzes the effects of dilute D-instantons in type-IIB string thermodynamics, highlighting their role in phase transitions and singularities at finite temperature.

Contribution

It provides a detailed study of D-instanton effects on string thermodynamics, including the normalization of instanton measures and their impact on phase transition behavior.

Findings

D-instantons cause thermal singularities due to tachyonic winding modes.

Purely bosonic D-instantons induce infrared singularities affecting weak-coupling expansion.

Type-IIB D-instantons contribute smoothly at the Hagedorn temperature, not altering the phase transition order.

Abstract

We discuss Dirichlet instanton effects on type-IIB string Thermodynamics. We review some general properties of dilute D-instanton gases and use the low-energy supergravity solutions to define the normalization of the instanton measure, as well as the effects of long-range interactions. Thermal singularities in the single-instanton sector are due to tachyonic winding modes of Dirichlet open strings. Purely bosonic D-instantons induce in this way hard infrared singularities that ruin the weak-coupling expansion in the microcanonical ensemble. However, type-IIB D-instantons, give smooth contributions at the Hagedorn temperature, and the induced mass and coupling of the axion field are insufficient to change the first-order character of the phase transition in the mean field approximation.