  The study of QCD at finite baryon density is severely hampered by the
so-called fermion sign problem. As a result, we have no known first principles
approach to study nuclear matter, or neutron stars from QCD. On the surface,
the large Nc limit does not seem to simplify matters. In this limit, however,
one can exploit dualities that exist between strongly coupled gauge theories.
Our focus will be on some rather novel orbifold equivalences that have recently
been discovered at finite density. These equivalences relate strongly coupled
theories plagued by a sign problem, to strongly coupled theories free of sign
problems. As a result, such dualities give deeper insight into the nature of
the sign problem and possibly provide a way to simulate QCD at finite density
in the large Nc limit.
