1,466 research outputs found
Mass-radius constraints for compact stars and a critical endpoint
We present two types of models for hybrid compact stars composed of a quark
core and a hadronic mantle with an abrupt first order phase transition at the
interface which are in accordance with the latest astrophysical measurements of
two 2 M_sun pulsars. While the first is a schematic one, the second one is
based on a QCD motivated nonlocal PNJL model with density-dependent vector
coupling strength. Both models support the possibility of so called twin
compact stars which have the same mass but different radius and internal
structure at high mass (~2 M_sun), provided they exhibit a large jump \Delta
\epsilon in the energy density of the first order phase transition fulfilling
\Delta \epsilon/\epsilon_crit > 0.6. We conclude that the measurement of
high-mass twin stars would support the existence of a first order phase
transition in symmetric matter at zero temperature entailing the existence of a
critical end point in the QCD phase diagram.Comment: 7 pages, 2 figures, 1 table, prepared for the Proceedings of the 8th
International Workshop on "Critical Point and Onset of Deconfinement",March
11 to 15, 2013, Napa, California, US
A New Approach to Non-Commutative U(N) Gauge Fields
Based on the recently introduced model of arXiv:0912.2634 for non-commutative
U(1) gauge fields, a generalized version of that action for U(N) gauge fields
is put forward. In this approach to non-commutative gauge field theories, UV/IR
mixing effects are circumvented by introducing additional 'soft breaking' terms
in the action which implement an IR damping mechanism. The techniques used are
similar to those of the well-known Gribov-Zwanziger approach to QCD.Comment: 11 pages; v2 minor correction
and mesons in the Dyson-Schwinger approach at finite temperature
We study the temperature dependence of the pseudoscalar meson properties in a
relativistic bound-state approach exhibiting the chiral behavior mandated by
QCD. Concretely, we adopt the Dyson-Schwinger approach with a rank-2 separable
model interaction. After extending the model to the strange sector and fixing
its parameters at zero temperature, T=0, we study the T-dependence of the
masses and decay constants of all ground-state mesons in the pseudoscalar
nonet. Of chief interest are and . The influence of the QCD
axial anomaly on them is successfully obtained through the Witten-Veneziano
relation at T=0. The same approach is then extended to T>0, using lattice QCD
results for the topological susceptibility. The most conspicuous finding is an
increase of the mass around the chiral restoration temperature
, which would suggest a suppression of production in
relativistic heavy-ion collisions. The increase of the mass may
also indicate that the extension of the Witten-Veneziano relation to finite
temperatures becomes unreliable around and above . Possibilities of
an improved treatment are discussed.Comment: 13 pages, 15 figure
Hadronic Spectral Function and Charm Meson Production
At the chiral restoration/deconfinement transition, most hadrons undergo a
Mott transition from being bound states in the confined phase to resonances in
the deconfined phase. We investigate the consequences of this qualitative
change in the hadron spectrum on final state interactions of charmonium in hot
and dense matter, and show that the Mott effect for D-mesons leads to a
critical enhancement of the J/Psi dissociation rate. Anomalous J/Psi
suppression in the NA50 experiment is discussed as well as the role of the Mott
effect for the heavy flavor kinetics in future experiments at the LHC. The
status of our calculations of hadron-hadron cross sections using the quark
interchange and chiral Lagrangian approaches is reviewed, and an Ansatz for a
unification of these schemes is given.Comment: 12 pages, 6 figures, Proceedings of the Budapest'02 Workshop on Quark
& Hadron Dynamics, Budapest, Hungary, March 3-7, 200
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