Finite isospin density probe for conformality

Abstract

A new method of employing an isospin chemical potential for QCD-like theories with different number of colors, number of fermion flavors, and in different fermion representations is proposed.The isospin chemical potential, which can be simulated on the lattice due to its positive definite determinant gives a means to probe both confining theories and IR conformal theories without adjusting the lattice spacing and size. As the quark mass is reduced, the isospin chemical potential provides an avenue to extract the chiral condensate in confining theories through the resulting pseudoscalar condensate. For IR conformal theories, the mass anomalous dimension can be extracted in the conformal window through "finite density" scaling since the isospin chemical potential is coupled to a conserved current. In both of these approaches, the isospin chemical potential can be continuously varied for each ensemble at comparable costs while maintaining the hierarchy between the lattice size and lattice spacing. In addition to exploring these methods, finite volume and lattice spacing effects are investigated.

Recent advances on chiral partners and patterns and the thermal f 0 ( 500 ) in chiral restoration

“…Thus, (2.1)) implies that in such O(4) degenerating scenario, χ 5.disc (and hence the topological susceptibility) should vanish as well, which supports the O(4) ×U(1) A pattern from the point of view of partner degeneration. This conclusion is consistent with the lattice works [9,10,11,12], while the discrepancy with [3] can be explained [14] by the large uncertainties in the degeneration of χ ll P − χ δ S compared to those in χ π P − χ ll S , visible in Fig. 1.…”

“…Note in particular that the susceptibility difference χ 5,disc = 1 4 χ π P − χ ll P is a measure of the O(4) ×U(1) A breaking. That particular combination is also interesting because it is proportional to the topological susceptibility measuring genuine anomalous effects [3]. Actually, in [3], for N f = 2 + 1 and physical quark masses, a sizable separation between the susceptibilities for the O(4) and U(1) A partners was obtained.…”

“…Furthermore, (2.2) allows one to parametrize the breaking of that degeneracy in the lattice, since the r.h.s is proportional to the subtracted quark condensate ∆ l,s = qq l − 2(m/m s ) ss , customarily used in lattice as a chiral order parameter in order to avoid finite size divergences in individual condensates [1,2,3].…”

“…Its experimental implications are also crucial for the Physics of Ultrarelativistic Heavy Ion Collisions. It has been already established that in the physical case of N f = 2 + 1 flavours withm m s masses, the chiral transition is a crossover at a transition temperature of about T c ∼ 155 − 160 MeV for vanishing baryon density [1,2,3]. The ideal chiral restoration phase transition is reached only for N f = 2 andm = 0, while in the physical case it is approached in the light chiral limitm → 0 + .…”

Effects of near-zero Dirac eigenmodes on axial U(1) symmetry at finite temperature

“…The JLQCD collaboration [3] and TWQCD collaboration [4] reported that U(1)A symmetry is restored above the critical temperature using the overlap and the optimal domain-wall fermions, respectively. On the other hand, LLNL/RBC collaboration [5,6] and Ohno et. al [7] obtained results that suggest the opposite conclusion using the domain-wall or staggered fermions.…”