Deconfinement transition in two-flavor lattice QCD with dynamical overlap fermions in an external magnetic field (original) (raw)
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2014
V. G. Bornyakov, 3 P. V. Buividovich, N. Cundy, O. A. Kochetkov, 2, ∗ and A. Schäfer Institute for High Energy Physics, 142281, Protvino, Russia Institute of Theoretical and Experimental Physics, 117259 Moscow, Russia Far Eastern Federal University, Sukhanova Street 8, Vladivostok 690950, Russia Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany Lattice Gauge Theory Research Center, FPRD, and CTP Department of Physics and Astronomy, Seoul National University,Seoul, 151-747, South Korea (Dated: August 15th, 2014)
QCD phase transition in a strong magnetic background
Physical Review D, 2010
We investigate the properties of the deconfining/chiral restoring transition for two flavor QCD in presence of a uniform background magnetic field. We adopt standard staggered fermions and a lattice spacing of the order of 0.3 fm. We explore different values of the bare quark mass, corresponding to pion masses in the range 200 -480 MeV, and magnetic fields up to |e|B ∼ 0.75 GeV 2 . The deconfinement and chiral symmetry restoration temperatures remain compatible with each other and rise very slightly (< 2% for our largest magnetic field) as a function of the magnetic field. On the other hand, the transition seems to become sharper as the magnetic field increases.
Physical Review D, 2011
We investigate the QCD phase diagram based on the strong coupling expansion of the lattice QCD with one species of the staggered fermions at finite temperature (T ) and chemical potential (µ). We analytically derive an effective potential including both chiral and deconfinement (Z N c ) dynamics with finite coupling effects in mean-field approximations. We focus on Polyakov loop properties in whole T − µ plane, and study relations between the chiral and deconfinement crossovers. At a fixed large µ, sequencial rapid variations of the Polyakov loop are observed with increasing T . It is natural to interprete them as the "chiral induced" and "Z N c induced" deconfinements crossovers.
Strong-coupling lattice study for QCD phase diagram including both chiral and deconfinement dynamics
We investigate the QCD phase diagram by using the strong-coupling expansion of the lattice QCD with one species of staggered fermion and the Polyakov loop effective action at finite temperature (T) and quark chemical potential (mu). We derive an analytic expression of effective potential Feff including both the chiral (U(1)) and the deconfinement (Z_Nc) dynamics with finite coupling effects in the mean-field approximation. The Polyakov loop increasing rate (dl/dT) is found to have two peaks as a function of T for small quark masses. One of them is the chiral-induced peak associated with the rapid decrease of the chiral condensate. The temperature of the other peak is almost independent of the quark mass or chemical potential, and this peak is interpreted as the Z_Nc-induced peak.
Physical Review D, 2010
The structure of the phase diagram for strong interactions becomes richer in the presence of a magnetic background, which enters as a new control parameter for the thermodynamics. Motivated by the relevance of this physical setting for current and future high-energy heavy ion collision experiments and for the cosmological QCD transitions, we use the linear sigma model coupled to quarks and to Polyakov loops as an effective theory to investigate how the chiral and the deconfining transitions are affected, and present a general picture for the temperature--magnetic field phase diagram. We compute and discuss each contribution to the effective potential for the approximate order parameters, and uncover new phenomena such as the paramagnetically-induced breaking of global Z_3 symmetry, and possible splitting of deconfinement and chiral transitions in a strong magnetic field.
Magnetic catalysis (and inverse catalysis) at finite temperature in two-color lattice QCD
Physical Review D, 2014
Two-color lattice QCD with N f = 4 staggered fermion degrees of freedom (no rooting trick is applied) with equal electric charge q is studied in a homogeneous magnetic background field B and at non-zero temperature T. In order to circumvent renormalization as a function of the bare coupling we apply a fixed-scale approach. We study the influence of the magnetic field on the critical temperature. At rather small pseudo-scalar meson mass (mπ ≈ 175 MeV ≈ Tc(B = 0)) we confirm a monotonic rise of the quark condensate <ψψ > with increasing magnetic field strength, i.e. magnetic catalysis, as long as one is staying within the confinement or deconfinement phase. In the transition region we find indications for a non-monotonic behavior of Tc(B) at low magnetic field strength (qB < 0.8 GeV 2) and a clear rise at stronger magnetic field. The conjectured existence of a minimum value Tc(B *) < Tc(B = 0) would leave a temperature window for a decrease of <ψψ > with rising B (inverse magnetic catalysis) also in the present model.
The finite temperature QCD transition in external magnetic fields
2011
The effect of an external magnetic field on the finite temperature transition of QCD is studied. We measure thermodynamic observables including the quark condensates and susceptibilities and the strange quark number susceptibility. We generate configurations at various values of the quantized magnetic flux with N f = 2 + 1 flavors of stout smeared staggered quarks at physical quark masses. We perform the renormalization of our observables and approach the continuum limit with N t = 6, 8 and 10 lattices. We also check finite volume effects using various lattice volumes. Our main result is that the transition temperature significantly decreases with growing magnetic field, and that the transition remains an analytic crossover up to our largest external field √ eB ≈ 1 GeV.
Deconfinement phase transition in one-flavor QCD
Physical Review D, 1999
We present a study of the deconfinement phase transition of one-flavor QCD using the multiboson algorithm. The mass of the Wilson fermions relevant for this study is moderately large and the non-Hermitian multiboson method is a superior simulation algorithm. Finite-size scaling is studied on lattices of size 83×4, 123×4, and 163×4. The behaviors of the peak of the Polyakov loop
Deconfining transition in two-flavor QCD
Nuclear Physics B-proceedings Supplements, 2004
The order and the nature of the finite-temperature phase transition of QCD with two flavors of dynamical quarks is investigated. An analysis of the critical exponent of the specific heat is performed through finite-size and finite-mass scaling of various susceptibilities. Dual superconductivity of QCD vacuum is investigated using a disorder parameter, namely the v.e.v. of a monopole creation operator. Hybrid R simulations were run at lattice spatial sizes of 123, 163, 203 and 323 and temporal size Nt = 4, with quark masses in the range amq = 0.3 − 0.01.