4,503 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
Uniform semiclassical approximation in quantum statistical mechanics
We present a simple method to deal with caustics in the semiclassical
approximation to the partition function of a one-dimensional quantum system.
The procedure, which makes use of complex trajectories, is applied to the
quartic double-well potential.Comment: 5 pages, 1 figure, Latex. Contribution to the Proceedings of the XXI
Brazilian National Meeting on Particles and Fields (Sao Lourenco, October
23-27, 2000
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