In the large Nc limit, some apparently different gauge theories turn out to be equivalent due to large Nc orbifold equivalence. We use effective field theory techniques to explore orbifold equivalence, focusing on the specific case of a recently discovered relation between an SO(2N c) gauge theory and QCD. The equivalence to QCD has been argued to hold at finite baryon chemical potential, μB, so long as one deforms the SO(2Nc) theory by certain "double-trace" terms. The deformed SO(2Nc) theory can be studied without a sign problem in the chiral limit, in contrast to SU(Nc) QCD at finite μB. The purpose of the double-trace deformation in the SO(2Nc) theory is to prevent baryon number symmetry from breaking spontaneously at finite density, which is necessary for the equivalence to large Nc QCD to be valid. The effective field theory analysis presented here clarifies the physical significance of double-trace deformations, and strongly supports the proposed equivalence between the deformed SO(2Nc) theory and large N c QCD at finite density.
- 1/N Expansion
- Chiral Lagrangians
- Lattice Gauge Field Theories
- Spontaneous Symmetry Breaking