2,275 research outputs found
Thermodynamic instabilities in dynamical quark models with complex conjugate mass poles
We show that the CJT thermodynamic potential of dynamical quark models with a
quark propagator represented by complex conjugate mass poles inevitably
exhibits thermodynamic instabilities. We find that the minimal coupling of the
quark sector to a Polyakov loop potential can strongly suppress but not
completely remove such instabilities. This general effect is explicitly
demonstrated in the framework of a covariant, chirally symmetric, effective
quark model.Comment: Minor typos corrected, submitted versio
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
Hadronic correlations above the chiral/deconfinement transition
The statistical bootstrap model is critically revised in order to include a
medium-dependent resonance width in it. We show that a thermodynamic model with
a vanishing width below the Hagedorn temperature T_H and a Hagedorn
spectrum-like width above T_H may not only eliminate the divergence of the
thermodynamic functions above T_H, but also gives a satisfactory description
the lattice quantum chromodynamics (QCD) data on the energy density above the
chiral/deconfinement transition as the main result of this contribution. This
model allows to explain the absence of heavy resonance contributions in the fit
of the experimentally measured particle ratios at SPS and RHIC energies.Comment: 9 pages, 2 figures, contribution to proceedings of NAPP 2003,
Dubrovnik, Croatia, 26-31 May, 200
Mott-Anderson freeze-out and the strange matter "horn"
We discuss the -dependence of the ratio in heavy-ion
collisions (the "horn" effect) within a Mott-Anderson localization model for
chemical freeze-out. The different response of pion and kaon radii to the hot
and dense hadronic medium results in different freeze-out conditions. We
demonstrate within a simple model that this circumstance enhances the "horn"
effect relative to statistical models with universal chemical freeze-out.Comment: 8 pages, 4 figure
A Generalization of Slavnov-Extended Non-Commutative Gauge Theories
We consider a non-commutative U(1) gauge theory in 4 dimensions with a
modified Slavnov term which looks similar to the 3-dimensional BF model. In
choosing a space-like axial gauge fixing we find a new vector supersymmetry
which is used to show that the model is free of UV/IR mixing problems, just as
in the previously discussed model in arXiv:hep-th/0604154. Finally, we present
generalizations of our proposed model to higher dimensions.Comment: 25 pages, no figures; v2 minor correction
On Non-Commutative U*(1) Gauge Models and Renormalizability
Based on our recent findings regarding (non-)renormalizability of
non-commutative U*(1) gauge theories [arxiv:0908.0467, arxiv:0908.1743] we
present the construction of a new type of model. By introducing a soft breaking
term in such a way that only the bilinear part of the action is modified, no
interaction between the gauge sector and auxiliary fields occurs. Demanding in
addition that the latter form BRST doublet structures, this leads to a
minimally altered non-commutative U*(1) gauge model featuring an IR damping
behavior. Moreover, the new breaking term is shown to provide the necessary
structure in order to absorb the inevitable quadratic IR divergences appearing
at one-loop level in theories of this kind. In the present paper we compute
Feynman rules, symmetries and results for the vacuum polarization together with
the one-loop renormalization of the gauge boson propagator and the three-point
functions.Comment: 20 pages, 4 figures; v2-v4: clarified several points, and minor
correction
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