Statistical mechanics of null strings

Abstract

In this paper we study the behaviour of a gas of null (tensionless) strings from the point of view of statistical mechanics. The interest in the study of null strings, apart from the intrinsic one, lies in the connection that can be made between null strings and strings at the Hagedorn temperature. We find that free energy and pressure can be defined, although, even in the microcanonical approach, temperature and entropy cannot be properly introduced. We also calculate the equation of state for a gas of null strings, and find it to be similar to the one of a gas of massless particles.