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.
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.
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.
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)
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.
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.
59471827
Special Geometries Emerging from Yang-Mills Type Matrix Models
I review some recent results which demonstrate how various geometries, such as Schwarzschild and Reissner-Nordstrom, can emerge from Yang-Mills type matrix models with branes. Furthermore, explicit embeddings of these branes as well as appropriate Poisson structures and starproducts which determine the non-commutativity of space-time are provided. These structures are motivated by higher order terms in the effective matrix model action which semi-classically lead to an Einstein-Hilbert type action.
16048421
Gauge Theories on Deformed Spaces
The aim of this review is to present an overview over available models and approaches to non-commutative gauge theory. Our main focus thereby is on gauge models formulated on flat Groenewold-Moyal spaces and renormalizability, but we will also review other deformations and try to point out common features. This review will by no means be complete and cover all approaches, it rather reflects a highly biased selection.
16546446
On the problem of renormalizability in non‐commutative gauge field models – a critical review
AbstractWhen considering quantum ﬁeld theories on non-commutative spaces one inevitablyencounters the infamous UV/IR mixing problem. So far, only very few renormalizablemodels exist and all of them describe non-commutative scalar ﬁeld theories on four-dimensional Euclidean Groenewold-Moyal deformed space, also known as ‘θ-deformedspace’ R 4θ . In this work we discuss some major obstacles of constructing a renormalizablenon-commutative gauge ﬁeld model and sketch some possible ways out. 1 Introduction Ever since the ﬁrst non-commutative quantum ﬁeld theory models were constructed, thegreatest obstacle has been the infamous so-called UV/IR mixing problem [1], where certaintypes of Feynman graphs, the non-planar graphs, exhibit new unrenormalizable IR singular-ities in exceptional momenta (see [2, 3, 4] for a review). The situation improved dramaticallywhen the ﬁrst renormalizable scalar non-commutative model, the Grosse-Wulkenhaar model,was put forward [5, 6, 7]. Later, a second renormalizable scalar non-commutative quantumﬁeld theory was presented by Gurau
119279267
On non-commutative U⋆(1) gauge models and renormalizability
Based on our recent findings regarding (non-)renormalizability of non-commutative U(1) gauge theories [1, 2] 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 this paper we compute Feynman rules, symmetries and results for the vacuum polarization together with the one-loop renormalization of the gauge boson propagator and three-point functions.
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.