Q7-branes and their coupling to IIB supergravity

TL;DR

This paper introduces a new classification of 7-branes in IIB supergravity based on SL(2,R) conjugacy classes, constructing their couplings and Wess-Zumino terms, and revealing a new family called Q7-branes.

Contribution

It provides a novel basis for classifying 7-branes in IIB supergravity and constructs their gauge-invariant couplings, including the full bosonic Wess-Zumino term.

Findings

Q7-branes are characterized by an SL(2,R) charge matrix Q with detQ > 0.

The conjugacy classes are determined by the determinant of Q, with (p,q) 7-branes at detQ=0.

A gauge-invariant coupling involves an SL(2,R) doublet of Born-Infeld fields.

Abstract

We show how, by making use of a new basis of the IIB supergravity axion-dilaton coset, SL(2,R)/SO(2), 7-branes that belong to different conjugacy classes of the duality group SL(2,R) naturally couple to IIB supergravity with appropriate source terms characterized by an SL(2,R) charge matrix Q. The conjugacy classes are determined by the value of the determinant of Q. The (p,q) 7-branes are the branes in the conjugacy class detQ = 0. The 7-branes in the conjugacy class detQ > 0 are labelled by three numbers (p,q,r) which parameterize the matrix Q and will be called Q7-branes. We construct the full bosonic Wess--Zumino term for the Q7-branes. In order to realize a gauge invariant coupling of the Q7-brane to the gauge fields of IIB supergravity it is necessary to introduce an SL(2,R) doublet of two distinct Born--Infeld fields on the Q7-brane world-volume.