6,012 research outputs found
QCD under extreme conditions: an informal discussion
We present an informal discussion of some aspects of strong interactions
under extreme conditions of temperature and density at an elementary level.
This summarizes lectures delivered at the 2013 CERN -- Latin-American School of
High-Energy Physics and is aimed at students working in experimental
high-energy physics.Comment: 11 pages, 6 figures, based on lectures at the 2013 CERN --
Latin-American School of High-Energy Physics, Arequipa, Peru, submitted for
publication in a CERN Yellow Repor
Weinberg power counting and the quark determinant at small chemical potential
We construct an effective action for QCD by expanding the quark determinant
in powers of the chemical potential at finite temperature in the case of
massless quarks. To cut the infinite series we adopt the Weinberg power
counting criteria. We compute the minimal effective action (~p^4), expanding in
the external momentum, which implies the use of the hard thermal loop
approximation. Our main result is a gauge invariant expression for the phase
theta of the functional determinant in QCD, and recovers dimensional reduction
in the high-temperature limit. We compute, analytically, in the range
of p << 2 pi T, including perturbative and nonperturbative contributions, the
latter treated within the mean field approximation. Implications for lattice
simulations are briefly discussed.Comment: 5 pages, 2 figures. v2: title changed, expanded discussion and added
example (calculation of at high temperature). Published in PR
A search for inverse magnetic catalysis in thermal quark-meson models
We explore the parameter space of the two-flavor thermal quark-meson model
and its Polyakov loop-extended version under the influence of a constant
external magnetic field . We investigate the behavior of the pseudo critical
temperature for chiral symmetry breaking taking into account the likely
dependence of two parameters on the magnetic field: the Yukawa quark-meson
coupling and the parameter of the Polyakov loop potential. Under the
constraints that magnetic catalysis is realized at zero temperature and the
chiral transition at is a crossover, we find that the quark-meson model
leads to thermal magnetic catalysis for the whole allowed parameter space, in
contrast to the present picture stemming from lattice QCD.Comment: 8 pages, 5figure
The role of noise and dissipation in the hadronization of the quark-gluon plasma
We discuss the role of noise and dissipation in the explosive spinodal
decomposition scenario of hadron production during the chiral transition after
a high-energy heavy ion collision. We use a Langevin description inspired by
nonequilibrium field theory to perform real-time lattice simulations of the
behavior of the chiral fields. Preliminary results for the interplay between
additive and multiplicative noise terms, as well as for non-Markovian
corrections, are also presented.Comment: 8 pages, invited talk at the Workshop on Quark Gluon Plasma
Thermalization, Vienna, August 10-12, 200
On thermal nucleation of quark matter in compact stars
The possibility of a hadron-quark phase transition in extreme astrophysical
phenomena such as the collapse of a supernova is not discarded by the modern
knowledge of the high-energy nuclear and quark-matter equations of state. Both
the density and the temperature attainable in such extreme processes are
possibly high enough to trigger a chiral phase transition. However, the time
scales involved are an important issue. Even if the physical conditions for the
phase transition are favorable (for a system in equilibrium), there may not be
enough time for the dynamical process of phase conversion to be completed. We
analyze the relevant time scales for the phase conversion via thermal
nucleation of bubbles of quark matter and compare them to the typical
astrophysical time scale, in order to verify the feasibility of the scenario of
hadron-quark phase conversion during, for example, the core-collapse of a
supernova.Comment: 6 pages, 4 figures, talk given at the International Conference
SQM2009, Buzios, Rio de Janeiro, Brazil, Sep.27-Oct.2, 200
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