D branes in string theory, II

TL;DR

The work develops a unified boundary-state formalism to describe dynamical D-branes, including boosted and rotated configurations, branes with world-volume abelian fields, and T-duality-induced transverse excitations. It shows how the boundary state framework reproduces the Dirac-Born-Infeld action and Wess-Zumino couplings, derives long-range field profiles, and constructs bound states such as (F,D$p$) with explicit harmonic-function solutions. It further extends to compactified settings and finally builds a boundary-state description of stable non-BPS states in type I via D1–anti-D1 systems with Wilson lines, illustrating non-perturbative duality with the SO(32) heterotic string. Together, these results demonstrate the boundary-state approach as a powerful, gauge-invariant tool for encoding brane dynamics, bound states, and dualities in string theory.

Abstract

In these lectures we review the properties of a boosted and rotated boundary state and of a boundary state with an abelian gauge field deriving from it the Dirac-Born-Infeld action and a newly constructed class of classical solutions. We also review the construction of the boundary state for the stable non-BPS state of type I theory corresponding to the perturbative state present at the first excited level of the SO(32) heterotic string and transforming according to the spinor representation of SO(32) (Lectures presented at the YITP Workshop on ``Developments in Superstring and M-theory'', Kyoto, Japan, October 1999).