Rolling of Modulated Tachyon with Gauge Flux and Emergent Fundamental String

TL;DR

This paper explores the real-time dynamics of unstable D-branes with fundamental string charge, revealing how spatial modulation and gauge fields influence string formation and distribution during decay.

Contribution

It constructs a boundary state for modulated tachyon rolling with gauge fields and analyzes the resulting string charge distribution and dynamics, including BPS-like string formation.

Findings

Spatial modulation triggers density waves of strings and anti-strings.

Energy density and string charge density form localized delta-function arrays.

Fundamental strings become BPS-like near the critical gauge field limit.

Abstract

We investigate real-time tachyon dynamics of unstable D-brane carrying fundamental string charge. We construct the boundary state relevant for rolling of modulated tachyon with gauge fields excited on the world-volume, and study spatial distribution of the fundamental string charge and current as the D-brane decays. We find that, in contrast to homogeneous tachyon rolling, spatial modulation of the tachyon field triggers density wave of strings when electric field is turned on, and of string anti-string pairs when 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 initial condition of rolling tachyon. 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.