Confinement and Strings in MQCD

TL;DR

This paper investigates confinement mechanisms in MQCD, demonstrating how heavy quarks form bound states and analyzing the transition from N=2 to N=1 theories, revealing string tension ratios and monopole confinement features.

Contribution

It provides a detailed analysis of confinement in MQCD, including the behavior of strings and mesons during the transition from N=2 to N=1 supersymmetry.

Findings

Heavy quarks are confined in hadrons as membrane-fivebrane bound states.

Most mesons disappear in the N=1 limit, but strings persist.

String tension ratios are consistent across N=2, N=1, and non-supersymmetric MQCD.

Abstract

We study aspects of confinement in the M theory fivebrane version of QCD (MQCD). We show heavy quarks are confined in hadrons (which take the form of membrane-fivebrane bound states) for N=1 and softly broken N=2 SU(Nc) MQCD. We explore and clarify the transition from the exotic physics of the latter to the standard physics of the former. In particular, the many strings and quark-antiquark mesons found in N=2 field theory by Douglas and Shenker are reproduced. It is seen that in the N=1 limit all but one such meson disappears while all of the strings survive. The strings of softly broken N=2, N=1, and even non-supersymmetric SU(Nc) MQCD have a common ratio for their tensions as a function of the amount of flux they carry. We also comment on the almost BPS properties of the Douglas-Shenker strings and discuss the brane picture for monopole confinement on N=2 QCD Higgs branches.