Rolling of a modulated tachyon with gauge flux and an emergent fundamental string

Abstract

We investigate the real-time tachyon dynamics of an unstable D-brane carrying fundamental string charge. We construct the boundary state relevant for the rolling of the modulated tachyon with gauge fields excited on the world volume, and study the spatial distribution of the fundamental string charge and current as the D-brane decays. We find that, in contrast with homogeneous tachyon rolling, spatial modulation of the tachyon field triggers a density wave of strings when the electric field is turned on and string-antistring pairs when the magnetic field is turned on. We show that the energy density and the fundamental string charge density are locked together and evolve into a localized delta-function array (instead of evolving into a string fluid) until a critical time set by the rolling tachyon's initial condition. When the gauge fields approach the critical limit, the fundamental strings produced become BPS-like. We also study the dynamics via effective field theory, and find agreement.