129 research outputs found
Recent Theoretical Developments in the QCD Phase Diagram
In this talk I discuss three recent developments in the theoretical
understanding of the phase diagram of the strong interaction. The first topic
deals with the comparison of model calculations of the quark-hadron transition
at vanishing quark chemical potential with state-of-the-art lattice QCD
results. In the second relates to the size of a possible 'quarkyonic phase'.
The third deals with the occurence of inhomogeneous chiral phases.Comment: 9 pages, 11 figures, proceedings for the International Workshop on
Hot and Cold Baryonic Matter 2010, Budapest, Aug. 15-20, 201
QCD thermodynamics with effective models
In this talk we extend the Polyakov-quark-meson model to N_f=2+1 quark
flavors and study its bulk thermodynamics at finite temperatures in mean-field
approximation. Three different Polyakov-loop potentials are considered. Our
findings are confronted to recent QCD lattice simulations of the RBC-Bielefeld
and HotQCD collaborations. Furthermore, the finite chemical potential expansion
of the quark-number susceptibility in a Taylor series around vanishing chemical
potential is analyzed. By means of a novel algorithmic differentiation
technique, we have calculated Taylor coefficients up to 24th order in the model
for the first time. This allows the systematic study of convergence properties
of the Taylor series.Comment: [references added]; 10 pages, 5 figures, talk given at the workshop
CPOD 2009, June 08 - 12, BNL, US
QCD Thermodynamics: Confronting the Polyakov-Quark-Meson Model with Lattice QCD
NJL-type effective models represent a low-energy realization of QCD and
incorporate pertinent aspects such as chiral symmetry and its spontaneous
breaking, the center symmetry in the heavy-quark limit as well as the axial
anomaly. One such model, the Polyakov-quark-meson model for three light quark
flavors, is introduced in order to study the phase structure of
strongly-interacting matter. With recent high-statistics lattice QCD
simulations of the finite-temperature equation of state, a detailed comparison
with model results becomes accessible. Such comparisons allow to estimate
volume and truncation effects of quantities, obtained on the lattice and
provide possible lattice extrapolation procedures to finite chemical potential
which are important to locate a critical endpoint in the QCD phase diagram.Comment: 10 pages, 4 figures, contributed to the proceedings of the EMMI
Workshop and XXVI Max Born Symposium at 09th-11th of July 2009 in Wroclaw,
Polan
Dyson-Schwinger study of chiral density waves in QCD
The formation of inhomogeneous chiral condensates in QCD matter at nonzero
density and temperature is investigated for the first time with Dyson-Schwinger
equations. We consider two massless quark flavors in a so-called chiral density
wave, where scalar and pseudoscalar quark condensates vary sinusoidally along
one spatial dimension. We find that the inhomogeneous region covers the major
part of the spinodal region of the first-order phase transition which is
present when the analysis is restricted to homogeneous phases. The triple point
where the inhomogeneous phase meets the homogeneous phases with broken and
restored chiral symmetry, respectively, coincides, within numerical accuracy,
with the critical point of the homogeneous calculation. At zero temperature,
the inhomogeneous phase seems to extend to arbitrarily high chemical
potentials, as long as pairing effects are not taken into account.Comment: 5 pages, 4 figures; v2: few minor modifications, matches published
versio
On the unlocking of color and flavor in color-superconducting quark matter
The role of the strange quark mass for the phase structure of QCD at
non-vanishing densities is studied by employing a recently developed
self-consistent truncation scheme for the Dyson-Schwinger equations of the
quark propagators in Landau gauge. Hereby the medium modification of the
effective quark interaction by the polarization of gluons is implemented.
Taking into account this effect results in significantly smaller dynamical
quark masses at the Fermi surface. Due to this reduction the color-flavor
locked phase is always the preferred color-superconducting phase at zero
temperature and for a realistic strange quark mass.Comment: 14 pages, 8 figure
Neutrality of the color-flavor-locked phase in a Dyson-Schwinger approach
The role of neutrality constraints for the phase structure of QCD at
non-vanishing chemical potentials is studied within a self-consistent
truncation scheme for the Dyson-Schwinger equation of the quark propagator in
Landau gauge. We find the (approximate) color-flavor-locked phase to be
energetically preferred at all potentially relevant densities and for physical
values of the quark masses. We furthermore observe the impossibility to define
this phase by residual global symmetries and discuss the role of chemical
potentials.Comment: 10 pages, 4 figure
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