We investigate the phase structure of QCD at finite temperature and
light-quark chemical potential. We improve upon earlier results for N_f=2+1
dynamical quark flavors and investigate the effects of charm quarks in an
extension to N_f=2+1+1. We determine the quark condensate and the Polyakov loop
potential using solutions of a coupled set of (truncated) Dyson-Schwinger
equations for the quark and gluon propagators of Landau gauge QCD. At zero
chemical potential we find excellent agreement with results from lattice-QCD.
With input fixed from physical observables we find only a very small influence
of the charm quark on the resulting phase diagram at finite chemical potential.
We discuss the location of the emerging critical end-point and compare with
expectations from lattice gauge theory.Comment: 10 pages, 9 figures, v2: typos corrected, minor changes, version
accepted by PR
We investigate the phase structure of QCD at finite temperature and chemical
potential by solving a coupled set of truncated Dyson-Schwinger equations for
the quark and gluon propagator. In contrast to previous calculations we take
into account the full back-reaction of the quarks onto the Yang-Mills sector
and we include the effects of strange quarks. We discuss the resulting thermal
mass of the unquenched gluon propagator and extract order parameters for the
chiral and deconfinement transition from the quarks. Our result for the
temperature dependence of the quark condensate at zero chemical potential
agrees well with corresponding lattice calculations. We determine the phase
diagram at finite chemical potential and find a potential critical endpoint at
(mu_q,T) = (190,100) MeV.Comment: 11 pages, 9 figures, 1 tabl
We present results for the chiral and deconfinement transition of two flavor QCD at finite temperature and chemical potential. To this end we study the quark condensate and its dual, the dressed Polyakov loop, with functional methods using a set of Dyson-Schwinger equations. The quark-propagator is determined self-consistently within a truncation scheme including temperature and in-medium effects of the gluon propagator. For the chiral transition we find a crossover turning into a first order transition at a critical endpoint at large quark chemical potential, µEP /TEP ≈ 3. For the deconfinement transition we find a pseudo-critical temperature above the chiral transition in the crossover region but coinciding transition temperatures close to the critical endpoint.
The Polyakov loop potential serves to distinguish between the confined
hadronic and the deconfined quark-gluon plasma phases of QCD. For Nf=2+1 quark
flavors with physical masses we determine the Polyakov loop potential at finite
temperature and density and extract the location of the deconfinement
transition. We find a cross-over at small values of the chemical potential
running into a critical end-point at mu/T > 1.Comment: 5 pages, 9 figure
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