Diquark condensation in dense adjoint matter

TL;DR

This paper investigates SU(2) lattice gauge theory with adjoint quarks at finite chemical potential, revealing a superfluid phase in the positive determinant sector and highlighting the challenges posed by the sign problem in exploring the full model.

Contribution

It provides the first numerical analysis of diquark condensation in adjoint matter at non-zero chemical potential, including the effects of the sign problem.

Findings

Positive determinant sector shows superfluid behavior with diquark condensation.

Agreement with chiral perturbation theory predictions.

Sign problem prevents full exploration of the onset transition.

Abstract

We study SU(2) lattice gauge theory at non-zero chemical potential with one staggered quark flavor in the adjoint representation. In this model the fermion determinant, although real, can be both positive and negative. We have performed numerical simulations using both hybrid Monte Carlo and two-step multibosonic algorithms, the latter being capable of exploring sectors with either determinant sign. We find that the positive determinant sector behaves like a two-flavor theory, with the chiral condensate rotating into a two-flavor diquark condensate for mu>m_pi/2, implying a superfluid ground state. Good agreement is found with analytical predictions made using chiral perturbation theory. In the `full' model there is no sign of either onset of baryon density or diquark condensation for the range of chemical potentials we have considered. The impact of the sign problem has prevented us from exploring the true onset transition and the mode of diquark condensation, if any, for this model.