119103336
Investigating the one-photon annihilation channel in an e-e+ plasma created from vacuum in strong laser fields
It is well known that in the presence of strong external electromagnetic fields many processes forbidden in standard QED become possible. One example is the one-photon annihilation process considered recently by the present authors in the framework of a kinetic approach to the quasiparticle e-e+ gamma plasma created from vacuum in the focal spot of two counter-propagating laser beams. In these works the domain of large values of the adiabaticity parameter gamma >> 1 (corresponding to multiphoton processes) was considered. In the present work we estimate the intensity of the radiation stemming from photon annihilation in the framework of the effective mass model where gamma < 1, corresponding to large electric fields E < E_c=m^2/e and high laser field frequencies (the domain characteristic for X-ray lasers of the next generation). Under such limiting conditions the resulting effect is sufficiently large to be accessible to experimental observation.
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.
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.
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.
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.
1425207
Divergences in non-commutative gauge theories with the Slavnov term
The divergence structure of non-commutative gauge field theories (NCGFT) with a Slavnov extension [1],[2] is examined at one-loop level with main focus on the gauge boson self-energy. Using an interpolating gauge we show that even with this extension the quadratic IR divergence of the gauge boson self-energy is independent from a covariant gauge fixing as well as from an axial gauge. The proposal of Slavnov is based on the fact that the photon propagator shows a new transversality condition with respect to the IR dangerous terms. This novel transversality is implemented with the help of a new dynamical multiplier field. However, one expects that in physical observables such contributions disappear. A further new feature is the existence of new UV divergences compatible with the gauge invariance (BRST symmetry). We then examine two explicit models with couplings to fermions and scalar fields.
119252029
BPHZ renormalization and its application to non-commutative field theory
In a recent work a modified BPHZ scheme has been introduced and applied to one-loop Feynman graphs in non-commutative ϕ4-theory. In the present paper, we first review the BPHZ method and then we apply the modified BPHZ scheme as well as Zimmermann’s forest formula to the sunrise graph, i.e. a typical higher-loop graph involving overlapping divergences. Furthermore, we show that the application of the modified BPHZ scheme to the IR-singularities appearing in non-planar graphs (UV/IR mixing problem) leads to the introduction of a 1/p2 term and thereby to a renormalizable model. Finally, we address the application of this approach to gauge field theories.
17839625
A Vector Supersymmetry Killing the Infrared Singularity of Gauge Theories in Noncommutative Space
We show that the ”topological BF-type” term introduced by Slavnov in order to cure the infrared divergences of gauge theories in noncommutative space can be characterized as the consequence of a new symmetry. This symmetry is a supersymmetry, generated by vector charges, of the same type as the one encountered in Chern-Simons or BF topological theories.
118514407
On the renormalization of non-commutative field theories
This paper addresses three topics concerning the quantization of non-commutative field theories (as defined in terms of the Moyal star product involving a constant tensor describing the non-commutativity of coordinates in Euclidean space). To start with, we discuss the Quantum Action Principle and provide evidence for its validity for non-commutative quantum field theories by showing that the equation of motion considered as insertion in the generating functional Zc[j] of connected Green functions makes sense (at least at one-loop level). Second, we consider the generalization of the BPHZ renormalization scheme to non-commutative field theories and apply it to the case of a self-interacting real scalar field: Explicit computations are performed at one-loop order and the generalization to higher loops is commented upon. Finally, we discuss the renormalizability of various models for a self-interacting complex scalar field by using the approach of algebraic renormalization.