Year: 2019
Type: article
Abstract: Using numerical simulations of lattice QCD with physical quark masses, we reveal the influence of magnetic-field background on chiral and deconfinement crossovers in finite-temperature QCD at low baryonic density. In the absence of thermodynamic singularity, we identify these transitions with inflection points of the approximate order parameters: normalized light-quark condensate and renormalized Polyakov loop, respectively. We show that the quadratic curvature of the chiral transition temperature in the ``temperature--chemical potential'' plane depends rather weakly on the strength of the background magnetic field. At weak magnetic fields, the thermal width of the chiral crossover gets narrower as the density of the baryon matter increases, possibly indicating a proximity to a real thermodynamic phase transition. Remarkably, the curvature of the chiral thermal width flips its sign at $e{B}_{\mathrm{fl}}\ensuremath{\simeq}0.6\text{ }\text{ }{\mathrm{GeV}}^{2}$, so that above the flipping point $B>{B}_{\mathrm{fl}}$, the chiral width gets wider as the baryon density increases. Approximately at the same strength of magnetic field, the chiral and deconfining crossovers merge together at $T\ensuremath{\approx}140\text{ }\text{ }\mathrm{MeV}$. The phase diagram in the parameter space ``temperature-chemical potential-magnetic field'' is outlined, and single-quark entropy and single-quark magnetization are explored. The curvature of the chiral thermal width allows us to estimate an approximate position of the chiral critical end point at zero magnetic field: $({T}_{c}^{\mathrm{CEP}},{\ensuremath{\mu}}_{B}^{\mathrm{CEP}})=(100(25)\text{ }\text{ }\mathrm{MeV},800(140)\text{ }\text{ }\mathrm{MeV})$. These results are based on numerical simulations performed mainly at the lattice time extension ${N}_{t}=6$.
Institutions: Moscow Institute of Physics and Technology, Far Eastern Federal University, Joint Institute for Nuclear Research, Université de Tours, Université d'Orléans, Centre National de la Recherche Scientifique, Institut Denis Poisson, Kurchatov Institute, Institute for Theoretical and Experimental Physics, Swansea University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W2974256964