Abstract
We study SU(2) lattice gauge theory with two flavors of Wilson fermion at non-zero chemical potential μ and low temperature on a 83×16 system. We identify three régimes along the μ-axis. For μ≲mπ/2 the system remains in the vacuum phase and all physical observables considered remain essentially unchanged. The intermediate régime is characterised by a non-zero diquark condensate and an associated increase in the baryon density, consistent with what is expected for Bose–Einstein condensation of tightly bound diquarks. We also observe screening of the static quark potential here. In the high-density deconfined régime we find a non-zero Polyakov loop and a strong modification of the gluon propagator, including significant screening in the magnetic sector in the static limit, which must have a non-perturbative origin. The behaviour of thermodynamic observables and the superfluid order parameter are consistent with a Fermi surface disrupted by a BCS diquark condensate. The energy per baryon as a function of μ exhibits a minimum in the deconfined régime, implying that macroscopic objects such as stars formed in this theory are largely composed of quark matter.
Highlights
At large quark chemical potential μ, QCD is expected to undergo a transition from a confined nuclear matter phase to a deconfined quark matter phase, where the relevant degrees of freedom are quarks and gluons
It is generally believed that the quark matter phase at low temperature T is characterised by diquark condensation: pairing of quarks near the Fermi surface gives rise to a number of color superconducting phases [1,2,3,4]
These methods are being extended in the direction of higher μ and lower T, but it is not clear at what point they break down, beyond which only unphysical results will be obtained. Another approach is to study QCD-like theories where the fermion determinant remains real and positive even when μ = 0. These can be used as a laboratory for investigating gauge theories at high density and low temperature
Summary
At large quark chemical potential μ, QCD is expected to undergo a transition from a confined nuclear matter phase to a deconfined quark matter phase, where the relevant degrees of freedom are quarks and gluons. Another approach is to study QCD-like theories where the fermion determinant remains real and positive even when μ = 0 These can be used as a laboratory for investigating gauge theories at high density and low temperature. Simon Hands et al.: Deconfinement in dense 2-color QCD not been investigated in any further detail, and it remains unclear whether there is a confined nuclear matter phase with non-zero baryon number (as in QCD), or just a single phase transition. This will be investigated in the present paper. On the other hand one has to contend with a higher computational cost, and for this reason, only a few studies using Wilson fermions have been performed to date [11]
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