SO(32) Spinors of Type I and Other Solitons on Brane-Antibrane Pair

TL;DR

This work constructs the SO(32) spinor state of type I string theory as a tachyonic kink on a D-string/anti-D-string pair, showing its mass scales as m_spinor ~ 1/g and providing an exact BCFT description at a critical radius where the tachyon mode is marginal. The BCFT analysis reveals the spinor state as a non-supersymmetric D0-brane, with the infinite-radius limit mapping to a D0 in type I and preserving SO(9) symmetry after dualities. The paper also demonstrates that this framework generalizes to vortex solutions on membrane–anti-membrane pairs (yielding type IIA D0-branes) and to D5–anti-D5 pairs (yielding type I D-strings), thereby presenting a unifying approach to solitons on brane–antibrane pairs and their various dual interpretations.

Abstract

We construct the SO(32) spinor state in weakly coupled type I string theory as a kink solution of the tachyon field on the D-string - anti-D-string pair and calculate its mass. We also give a description of this system in terms of an exact boundary conformal field theory and show that in this description this state can be regarded as a non-supersymmetric D0-brane in type I string theory. This construction can be generalised to represent the D0-brane in type IIA string theory as a vortex solution of the tachyon field on the membrane anti-membrane pair, and the D-string of type I string theory as a topological soliton of the tachyon field on the D5-brane anti- D5-brane pair.