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.
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.
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.
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.
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.
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.
118438417
Charmonium suppression at RHIC and SPS: A hadronic baseline
Abstract A kinetic equation approach is applied to model anomalous J / ψ suppression at RHIC and SPS by absorption in a hadron resonance gas which successfully describes statistical hadron production in both experiments. The puzzling rapidity dependence of the PHENIX data is reproduced as a geometric effect due to a longer absorption path for J / ψ production at forward rapidity.
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.
14510605
Conformal Relativity versus Brans-Dicke and Superstring Theories
We show how conformal relativity is related to Brans–Dicke theory and to low-energy-effective superstring theory. Conformal relativity or the Hoyle–Narlikar theory is invariant with respect to conformal transformations of the metric. We show that the conformal relativity action is equivalent to the transformed Brans–Dicke action for ω = -3/2 (which is the border between standard scalar field and ghost) in contrast to the reduced (graviton-dilaton) low-energy-effective superstring action which corresponds to the Brans–Dicke action with ω = -1. We show that like in ekpyrotic/cyclic models, the transition through the singularity in conformal cosmology in the string frame takes place in the weak coupling regime. We also find interesting self-duality and duality relations for the graviton-dilaton actions.
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.
118961690
Proving the CEP with compact stars
We present a model for hybrid compact stars composed of a quark core and a hadronic mantle with an abrupt first order phase transition at the interface and in accordance with the latest astrophysical measurements of two 2 M_sun pulsars. We demonstrate the possibility of a disconnected mass-radius sequence (third family) of high-mass pulsars as a distinct feature due to a large jump $\Delta \epsilon$ in the energy density of the first order phase transition setting in at $\epsilon_{\rm crit}\approx 500$ MeV/fm$^3$ and fulfilling $\Delta \epsilon/\epsilon_{\rm crit} > 0.6$. We conclude that the measurement of so called \textit{twin} compact stars at high mass (~ 2 M_sun) would support the existence of a first order phase transition in symmetric matter at zero temperature entailing the existence of a critical end point (CEP) in the QCD phase diagram.