119239913
Nonlocal quark model beyond mean field and QCD phase transition
Nonlocal chiral quark model is self-consistently extended beyond mean field using a strict 1 / N c expansion scheme. The parameters of the nonlocal model are refitted to the physical values of the pion mass and the weak pion decay constant. The size of the 1 / N c correction to the quark condensate is carefully studied in the nonlocal and the usual local Nambu–Jona-Lasinio models. It is found that even the sign of the corrections can be different. This can be attributed to the mesonic cut-off of the local model. It is also found that the 1 / N c corrections lead to lowering of the temperature of the chiral phase transition in comparison with the mean-field result. On the other hand, near the phase transition the 1 / N c expansion breaks down and a non-perturbative scheme for the inclusion of mesonic correlations is needed in order to describe the phase transition point.
5817770
Cooling of neutron stars with color superconducting quark cores
We show that within a recently developed nonlocal chiral quark model the critical density for a phase transition to color superconducting quark matter under neutron star conditions can be low enough for these phases to occur in compact star configurations with masses below 1.3 M ⊙ . We study the cooling of these objects in isolation for different values of the gravitational mass and argue that, if the quark matter phase would allow unpaired quarks, the corresponding hybrid stars would cool too fast. The comparison with observational data puts tight constraints on possible color superconducting quark matter phases. Possible candidates with diquark gaps of the order of 10 keV - 1 MeV such as the "2SC+X" and the color spin locking (CSL) phase are presented.
44204788
Chiral Condensate and Mott–Anderson Freeze-Out
We present the idea of a Mott–Anderson freeze-out that suggests a key role of the localization of the hadron wave functions when traversing the hadronization transition. The extension of hadron wave functions in dense matter is governed by the behavior of the chiral quark condensate such that its melting at finite temperatures and chemical potentials entails an increase of the size of hadrons and thus their geometrical strong interaction cross sections. It is demonstrated within a schematic resonance gas model, that a kinetic freeze-out condition reveals a correlation with the reduction of the chiral condensate in the phase diagram up to 50% of its vacuum value. Generalizing the description of the chiral condensate by taking into account a full hadron resonance gas such correlation gets distorted. We discuss, that this may be due to our approximations in calculating the chiral condensate which disregard both, in-medium effects on hadron masses and hadron–hadron interactions. The latter, in particular due to quark exchange reactions, could lead to a delocalization of the hadron wave functions in accordance with the picture of a Mott–Anderson transition.
119202592
Thermodynamic Instabilities in Dynamical Quark Models with Complex Conjugate Mass Poles
We show that the Cornwall-Jackiw-Tomboulis 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.
119222844
Kinetics of Photon Radiation off an e–e+-Plasma Created from the Vacuum in a Strong Laser Field
We consider the one-photon annihilation mechanism in a electron - positron quasiparticle plasma (EPP) created from the vacuum in a strong subcritical laser field due to the dynamical Schwinger mechanism. On the basis of a kinetic theory approach we show that the secondary photons have a radiation spectrum proportional to 1/k (flicker noise). This effect is very small for EPP excitations in the optical spectrum but can reach quite observable values in the γ -ray region (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
118475829
Chiral condensate and the structure of hadrons
A model of hadron masses based on the quark structure of hadrons combined with effects of chiral dynamics is used to calculate the 2+1 flavour chiral condensate in the hadron resonance gas framework. Results are discussed in the context of recent lattice QCD data. Improvements of the dynamical models of hadron structure are suggested with the aim to estimate the strange sigma term of the nucleon.
18811875
Quantum Corrections for Translation-Invariant Renormalizable Non-Commutative Phi**4 Theory
In this paper we elaborate on the translation-invariant renormalizable 4 theory in 4-dimensional non-commu\-ta\-tive space which was recently introduced by the Orsay group. By explicitly performing Feynman graph calculations at one loop and higher orders we illustrate the mechanism which overcomes the UV/IR mixing problem and ultimately leads to a renormalizable model. The obtained results show that the IR divergences are also suppressed in the massless case, which is of importance for the gauge field theoretic generalization of the scalar field model.
14134311
Improved localization of a renormalizable non-commutative translation invariant U(1) gauge model
Motivated by the recent work of Vilar et al. (arXiv:0902.2956) we enhance our non-commutative translation invariant gauge model (Blaschke D. N. et al., arXiv:0901.1681) by introducing auxiliary fields and ghosts forming a BRST doublet structure. In this way localization of the problematic term can be achieved without the necessity for any additional degrees of freedom. The resulting theory is suspected to be renormalizable. A rigorous proof, however, has not been accomplished up to now.
118497059
Gauge fields on non‐commutative spaces and renormalization
Constructing renormalizable models on non-commutative spaces constitutes a big challenge. Only few examples of renormalizable theories are known, such as the scalar Grosse-Wulkenhaar model. Gauge fields are even more difficult, since new renormalization techniques are required which are compatible with the inherently non-local setting on the one hand, and also allow to properly treat the gauge symmetry on the other hand. In this proceeding (which is based on my talk given at the “Workshop on Noncommutative Field Theory and Gravity” in Corfu/Greece, September 8–15, 2013), I focus on this last point and present new extensions to existing renormalization schemes (which are known to work for gauge field theories in commutative space) adapted to non-commutative Moyal space.
118528593
Slavnov-Taylor identities, non-commutative gauge theories and infrared divergences
A bstractIn this work we clarify some properties of the one-loop IR divergences in nonAbelian gauge field theories on non-commutative 4-dimensional Moyal space. Additionally, we derive the tree-level Slavnov-Taylor identities relating the two, three and four point functions, and verify their consistency with the divergent one-loop level results. We also discuss the special case of two dimensions.
3018752
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 [1] 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 problems, just as in the previously discussed model [2, 3]. Finally, we present generalizations of our proposed model to higher dimensions.