P-P' Strings in M(atrix) Theory

TL;DR

This paper demonstrates that the spectrum of off-diagonal blocks in M(atrix) theory, representing open strings between D-branes, matches string theory predictions and naturally includes degrees of freedom previously added by hand.

Contribution

It shows that off-diagonal zero modes in M(atrix) theory can be derived from the index theorem and supersymmetry, providing a natural description of string degrees of freedom.

Findings

Spectrum of off-diagonal zero modes matches string theory predictions.

Off-diagonal zero modes naturally include degrees of freedom for 0-4 strings.

Supersymmetry transformations and effective actions are derivable from M(atrix) theory.

Abstract

We study the off-diagonal blocks in the M(atrix) model that are supposed to correspond to open strings stretched between a Dp-brane and a Dp'-brane. It is shown that the spectrum, including the quantum numbers, of the zero modes in the off-diagonal blocks can be determined from the index theorem and unbroken supersymmetry, and indeed reproduces string theory predictions for p-p' strings. Previously the matrix description of a longitudinal fivebrane needed to introduce extra degrees of freedom corresponding to 0-4 strings by hand. We show that they are naturally associated with the off-diagonal zero modes, and the supersymmetry transformation laws and low energy effective action postulated for them are now derivable from the M(atrix) theory.