Phase diagram of dense two-color QCD within lattice simulations

Abstract

Abstract. We present the results of a low-temperature scan of the phase diagram of dense two-color QCD with N f = 2 quarks. The study is conducted using lattice simulation with rooted staggered quarks. At small chemical potential we observe the hadronic phase, where the theory is in a confining state, chiral symmetry is broken, the baryon density is zero and there is no diquark condensate. At the critical point µ = m π /2 we observe the expected second order transition to Bose-Einstein condensation of scalar diquarks. In this phase the system is still in confinement in conjunction with nonzero baryon density, but the chiral symmetry is restored in the chiral limit. We have also found that in the first two phases the system is well described by chiral perturbation theory. For larger values of the chemical potential the system turns into another phase, where the relevant degrees of freedom are fermions residing inside the Fermi sphere, and the diquark condensation takes place on the Fermi surface. In this phase the system is still in confinement, chiral symmetry is restored and the system is very similar to the quarkyonic state predicted by S U(N c ) theory at large N c .

Quarksonic matter at high isospin density

“…They call such a new phase of matter the "quarkyonic matter" which reflects the coexistence of quarks and baryons: the thermodynamic properties of the system are dominated by quark Fermi seas but the elementary fermionic excitations are confined baryons near the Fermi surfaces. Interestingly, recent LQCD simulation showed that even at N c = 2, the notion of quarkyonic matter is serviceable [14]. In this case, the LQCD found that the deconfinement never happens at zero temperature when µ B increases; instead, the system at large µ B is characterized by quarks always residing in Fermi seas and diquark condensate near the Fermi surface.…”

Study of the phase diagram of dense QC$_2$D with $N_f=2$ within lattice simulation

“…To study the phase diagram of QC 2 D with N f = 2 flavors we used a 16 3 × 32 lattice, simulating with β = 2.15, ma = 0.005, the lattice spacing a = 0.112(1) fm and the pion mass M π = 378(4) MeV (detailed description of the action and parameters may be found in [24]). …”

Some Relations for Quark Confinement and Chiral Symmetry Breaking in QCD

“…Also in N = 1 SUSY 1+3 QCD with N f = N c + 1, while confinement is realized, chiral symmetry breaking does not occur. A recent lattice study of SU(2)-color QCD with N f = 2 shows that a confined but chiral-restored phase is realized at a large baryon density [11]. Figure 1.…”