118487540
Extended BRST formulation of a non-commutative $U_*(1)$ gauge model
In this short letter, we rediscuss the model for non-commutative U⋆(1) gauge theory presented in [arXiv:0912.2634] and argue that by treating the ”soft-breaking terms” of that model in the realm of an extended BRST symmetry, a future renormalization proof using Algebraic Renormalization should be possible despite the fact that the non-commutative model is non-local. In fact, the non-localities could be treated in a way similar to commutative gauge theories with axial gauge fixing where certain non-local poles appear.
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.
16216330
A vector supersymmetry in noncommutative U(1) gauge theory with the Slavnov term
We consider noncommutative U(1) gauge theory with the additional term, involving a scalar field λ, introduced by Slavnov in order to cure the infrared problem. We show that this theory, with an appropriate space-like axial gauge-fixing, exhibits a linear vector supersymmetry similar to the one present in the 2-dimensional BF model. This vector supersymmetry implies that all loop corrections are independent of the λAA-vertex and thereby explains why Slavnov found a finite model for the same gauge-fixing.
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.
17541769
A vector supersymmetry killing IR divergences in non-commutative gauge theories
This is a report on the joint work with Francois Gieres, Stefan Hohenegger, Olivier Piguet and Manfred Schweda. We consider a non-commutative U(1) gauge theory with an extension which was originally proposed by A. A. Slavnov [3, 4] in order to get rid of UV/IR mixing problems. Here we show, that the improved IR behaviour of this model is mainly due to the appearence of a linear vector supersymmetry.
118634727
Loop calculations for the non-commutative U⋆(1) gauge field model with oscillator term
Motivated by the success of the non-commutative scalar Grosse–Wulkenhaar model, a non-commutative U⋆(1) gauge field theory including an oscillator-like term in the action has been put forward in (Blaschke et al. in Europhys. Lett. 79:61002, 2007). The aim of the current work is to analyze whether that action can lead to a fully renormalizable gauge model on non-commutative Euclidean space. In a first step, explicit one-loop graph computations are hence presented, and their results as well as necessary modifications of the action are successively discussed.
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.
14977007
Hybrid stars with color superconductivity within a nonlocal chiral quark model
Fachbereich Physik, Universit¨at Rostock, D-18051 Rostock, GermanyInstituto de F´isica Rosario, Bv. 27 de febrero 210 bis, 2000 Rosario, ArgentinaThe equation of state for quark matter is derived for a nonlocal, chiral quark model within themean ﬁeld approximation. Special emphasis is on the occurrence of a diquark condensate whichsignals a phase transition to color superconductivity and its eﬀects on the equation of state. Wepresent a ﬁt formula for the Bag pressure, which is densitiy dependent in case when the quarkmatter is color superconducting. We calculate the quark star conﬁgurations by solving the Tolman-Oppenheimer- Volkoﬀ equations and demonstrate the eﬀects of diquark condensation on the stabilityof hybrid stars for diﬀerent formfactors of the quark interaction.
54902612
Effective degrees of freedom in QCD thermodynamics
An effective model reproducing the equation of state of hadronic matter as ob- tained in recent lattice QCD simulations and from hadron resonance gas data is presented. The hadronic phase is described by means of an extended Mott-Hagedorn resonance gas while the QGP phase is described by the extended PNJL model. The dissociation of hadrons is obtained by including the state dependent hadron resonance width. The model gives a quantitative estimate for partial fractions of hadronic and partonic degrees of free- dom above Tc.
17180315
Phase diagram of neutron star quark matter in nonlocal chiral models
Abstract.We analyze the phase diagram of two-flavor quark matter under neutron star constraints for a nonlocal covariant quark model within the mean-field approximation. Applications to cold compact stars are discussed.
56263726
Mixed phase effects on high-mass twin stars
Recently it has been found that a certain class of hybrid star equations of state with a large latent heat (strong first order phase transition obtained by a Maxwell construction) between stiff hadronic and stiff quark matter phases allows for the appearance of a third family of compact stars (including “twins”) at high mass of ∼2 M⊙ We investigate how robust this high-mass twin phenomenon is against a smoothing of the transition which would occur, e.g., due to pasta structures in the mixed phase. To this end we propose a simple construction of a pasta-like equation of state with a parameter that quantifies the degree of smoothing of the transition and could eventually be related to the surface tension of the pasta structures. It is interesting to note that the range of energy densities for the transition as well as the pressure at the onset of the transition of this class of hybrid star matter at zero temperature corresponds well to values of the same quantities found in finite temperature lattice QCD simulations for the 1 σ region at the pseudocritical temperature Tc = 154 ± 9 MeV. The pattern of the speed of sound as a function of energy density is very different.