249 research outputs found
Color-Flavor (Un)locking
The structure of the phase diagram of strongly interacting matter at moderate
densities is calculated within a 3-flavor NJL-type quark model with realistic
quark masses. We focus on the influence of the selfconsistently determined
effective strange quark mass on the color-flavor unlocking phase transition.Comment: To appear in the proceedings of the workshop "Ultrarelativistic heavy
ion collisions", Hirschegg 2002, 6 page
Color superconductivity in two- and three-flavor systems at moderate densities
Basic features of color superconductivity are reviewed, focusing on the
regime of ``moderate densities'', which is not accessible by perturbation
theory. We discuss the standard picture of two- and three flavor color
superconductors and study the color-flavor unlocking phase transition within an
NJL-type model.Comment: 12 pages, 7 figures, to appear in: Proceedings of the NATO Advanced
Research Workshop on Confinement, Topology, and other Non-Perturbative
Aspects of QCD, Stara Lesna, Slovakia, Jan 21-27, 2002, references adde
Color-Flavor Unlocking and Phase Diagram with Self-Consistently Determined Strange Quark Masses
The phase diagram of strongly interacting matter at non-zero temperature and
baryon chemical potential is calculated within a 3-flavor NJL-type quark model
with realistic quark masses. The model exhibits spontaneous chiral symmetry
breaking as well as diquark condensation in the two-flavor
color-superconducting phase and in the color-flavor locked phase. We
investigate the color-flavor unlocking phase transition, taking into account
self-consistently calculated effective quark masses. We find that it is mainly
triggered by a first order phase transition with respect to the strange quark
mass. It takes place at much higher values of the chemical potential than the
transition to the hadronic phase such that we find a relatively large region in
the phase diagram where the two-flavor color-superconductor seems to be the
most favored state.Comment: 16 pages, 5 figures; v2: figure 2 of v1 removed, some changes in the
discussion, references adde
Mixed phases of color superconducting quark matter
We examine electrically and color neutral quark matter in beta-equilibrium
focusing on the possibility of mixed phases between different color
superconducting phases. To that end we apply the Gibbs criterion to ensure
phase equilibrium and discuss the external conditions under which these mixed
phases can occur. Neglecting surface and Coulomb effects we find a rich
structure of different mixed phases with up to four components, including 2SC
and CFL matter as well as more ``exotic'' components, like a phase with us- and
ds-pairing but without ud-pairing. Preliminary estimates indicate, however,
that the mixed phases become unstable if surface and Coulomb effects are
included.Comment: 22 pages, 9 figures, v2: minor changes in the text, version to appear
in Nucl. Phys.
Transport Properties of Strong-Interaction Matter
The properties of strong-interaction matter are probed in ultra-relativistic
heavy-ion collisions. In the context of measurements of the elliptic flow at
RHIC and the LHC the shear viscosity is of particular interest. In this
presentation we discuss recent results for eta/s in hadronic matter at
vanishing baryo-chemical potential within kinetic theory. Using the
Nambu-Jona-Lasinio model, special attention is paid to effects arising from the
restoration of spontaneously broken chiral symmetry with increasing
temperature.Comment: 8 pages, 4 figures, presented at the HIC for FAIR Workshop and XXVIII
Max Born Symposium "Three days on Quarkyonic Island", Wroclaw, May 19-21,
2011; v2: conversion to Pa in fig. 2 correcte
Momentum Dependence of the Pion Cloud for Rho Mesons in Nuclear Matter
We extend hadronic models for rho-meson propagation in cold nuclear matter
via coupling to in-medium pions to include finite three-momentum. Special care
is taken to preserve gauge invariance. Consequences for photoabsorption on the
proton and on nuclei as well as for the dilepton production in relativistic
heavy-ion collisions are discussed.Comment: 32 pages, 18 figures. Corrected version, accepted for publication in
Nucl. Phys.
A Microscopic Calculation of Photoabsorption Cross Sections on Protons and Nuclei
A recently developed model for -meson propagation in dense hadronic
matter is applied to total photoabsorption cross sections in -proton
and -nucleus reactions. Within the vector dominance model the photon
coupling to the virtual pion cloud of the nucleon, two-body meson-exchange
currents, as well as -nucleon resonances are included. Whereas the
reaction is determined by the low-density limit of the model, higher
orders in the nuclear density are important to correctly account for the
experimental spectra observed on both light and heavy nuclei over a wide range
of photon energies, including the region below the pion threshold. In
connection with soft dilepton spectra in high-energy heavy-ion collisions we
emphasize the importance of photoabsorption to further constrain the parameters
of the model.Comment: 10 pages RevTeX, 2 eps-figure
Quark Droplets in the NJL Mean Field
We study the conditions for the existence of stable quark matter in the
Nambu--Jona-Lasinio mean field at zero temperature and discuss its
interpretation.Comment: 6 pages, LaTeX, 4 eps-figures included, to appear in the Proc. of the
workshop 'QCD at Finite Baryon Density', Bielefeld, April 27-30, 199
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