Confinement and the quark Fermi surface in SU(2N) QCD-like theories

Yang-Mills theories with a gauge group SUâ¡(ð‘ð‘ ≠3) and quark matter in the fundamental representation share many properties with the theory of strong interactions, QCD with ð‘ð‘ =3. We show that, for ð‘ð‘ even and in the confinement phase, the gluonic average of the quark determinant is independent of the boundary conditions, periodic or antiperiodic ones. We then argue that a Fermi sphere of quarks can only exist under extreme conditions when the center symmetry is spontaneously broken and color is liberated. Our findings are supported by lattice gauge simulations for ð‘ð‘ =2-5 and are illustrated by means of a simple quark model.