On zero-point energy, stability and Hagedorn behavior of Type IIB strings on pp-waves

TL;DR

This paper investigates the zero-point energy and stability of Type IIB strings on pp-wave backgrounds, demonstrating their classical stability and well-defined thermodynamics, including Hagedorn behavior, after clarifying the calculation method.

Contribution

It provides a correct method for calculating zero-point energy and shows that these strings are stable with consistent thermal properties, addressing previous uncertainties.

Findings

Type IIB strings on pp-waves are classically stable.

They exhibit a well-defined Hagedorn temperature behavior.

The correct zero-point energy calculation resolves prior ambiguities.

Abstract

Type IIB strings on many pp-wave backgrounds, supported either by 5-form or 3-form fluxes, have negative light-cone zero-point energy. This raises the question of their stability and poses possible problems in the definition of their thermodynamic properties. After having pointed out the correct way of calculating the zero-point energy, an issue not fully discussed in literature, we show that these Type IIB strings are classically stable and have well defined thermal properties, exhibiting a Hagedorn behavior.