On T-Duality in Brane Gas Cosmology

TL;DR

This work extends the nonsingular cosmology afforded by T-duality in string gas models to brane gas cosmology within dilaton gravity. By explicitly implementing T-duality on a toroidal background with a gas of branes, the authors show that the brane gas mass spectrum is invariant under duality and that a temperature duality $T(R)=T(\alpha'/R)$ persists for adiabatic evolution, thereby arguing for a non-singular early Universe in brane gas scenarios. They derive brane energy, momentum, and pressure, establish the brane equation of state, and prove that the dual mass spectrum satisfies $M^*_{9-p}=M_p$ with a carefully related dual coupling $g^*$ and dual radii $R_n'$, including multiple winding configurations and string-brane mappings. The results generalize the Brandenberger-Veneziano mechanism to brane gases, suggesting a dynamical decompactification that yields three large spatial dimensions while respecting T-duality, and point to future work on oscillatory modes, gauge fields on branes, and backreaction effects.

Abstract

In the context of homogeneous and isotropic superstring cosmology, the T-duality symmetry of string theory has been used to argue that for a background space-time described by dilaton gravity with strings as matter sources, the cosmological evolution of the Universe will be nonsingular. In this Letter we discuss how T-duality extends to brane gas cosmology, an approximation in which the background space-time is again described by dilaton gravity with a gas of branes as a matter source. We conclude that the arguments for nonsingular cosmological evolution remain valid.