IIB or not IIB

TL;DR

This paper explores a variant of Type IIB superstring theory with added branes and anti-branes, analyzing its stability and relation to the standard IIB theory through tachyon dynamics.

Contribution

It introduces a new configuration of Type IIB superstring theory with branes and anti-branes without orientifolds, highlighting the resulting gauge group and instability.

Findings

The theory has a gauge group U(n) x U(n).

It exhibits a tachyonic instability due to brane-antibrane pairs.

The instability suggests a decay process toward the standard IIB theory.

Abstract

We consider Type IIB superstring theory with the addition of n 9-branes and n anti-9-branes (and no orientifolds). The result is a ten-dimensional chiral theory of open and closed oriented strings with gauge group U(n) \times U(n). There is, however, a tachyonic instability which can be understood as the consequence of brane-antibrane annihilation. We therefore expect to recover the usual IIB theory as the tachyon rolls to infinity.