Tachyon condensation in unstable type I D-brane systems

TL;DR

This paper analyzes the gauge groups and tachyon spectra of unstable D-brane systems in Type I string theory, revealing their vacuum structures and connections to real K-theory, and discusses the influence of background D9-branes.

Contribution

It classifies the gauge symmetry breaking patterns and vacuum topologies of all eight unstable D-brane systems in Type I string theory, linking them to real K-theory groups.

Findings

Determined gauge groups and tachyon spectra for all unstable D-branes.

Connected vacuum manifolds to real K-theory groups KO^{-n}.

Commented on the role of background D9-branes.

Abstract

Type I string theory provides eight classes of unstable D-brane systems. We determine the gauge group and tachyon spectrum for each one, and thereby describe the gauge symmetry breaking pattern in the low-energy world-volume field theory. The topologies of the resulting coset vacuum manifolds are related to the real K-theory groups KO^{-n}, extending the known relations between the Type II classifying spaces BU and U and the complex K-theory groups K^0 and K^{-1}. We also comment on the role of the background D9-branes.