We review our recent approach to non-extensive thermodynamics based on general composition rules. We discuss arguments in favor of using such an approach for quark matter due to momentum-dependent interaction and present first results of attempts to compute the equation of state of su2 gluon matter on a lattice in this non-extensive, generalized canonical framework.

Abstract.We calculate the variation with temperature of the vortex free energy in D=2+1 SU(2) lattice gauge theories. We do so both above and below the deconfining transition at T = T c . We find that this quantity is zero at all T for large enough volumes. For T < T c this observation is consistent with the fact that the phase is linearly confining; while for T > T c it is consistent with the conventional expectation of 'spatial' linear confinement. In small spatial volumes this quantity is shown to be non-zero. The way it decreases to zero with increasing volume is shown to be controlled by the (spatial) string tension and it has the functional form one would expect if the vortices being studied were responsible for the confinement at low T , and for the 'spatial' confinement at large T . We also discuss in detail some of the direct numerical evidence for a nonzero spatial string tension at high T , and we show that the observed linearity of the (spatial) potential extends over distances that are large compared to typical high-T length scales.

Varying the proposition that acceleration itself would simulate a thermal environment, we investigate the semiclassical photon radiation as a possible telemetric thermometer of accelerated charges. Based on the classical Jackson formula we obtain the equivalent photon intensity spectrum stemming from a constantly accelerated charge and demonstrate its resemblances to a thermal distribution for high transverse momenta. The inverse transverse slope differs from the famous Unruh temperature: it is larger by a factor of pi. We compare the resulting direct photon spectrum with experimental data for AuAu collisions at RHIC and speculate about further, analytically solvable acceleration histories.Comment: LaTeX 5 pages, 2 eps figures, PACS numbers: 24.10.Pa, 25.75.Ag, 25.20.Lj Keywords: Thermal models, Unruh temperature, bremsstrahlung, photon spectr

The authors review the various string models proposed to describe hadrons and their interactions. QCD and QCD-inspired phenomenological models motivated the development of a rather large variety of string models. Among others the Polyakov model, the Friedberg-Lee model, the MIT flux tube model, semirelativistic string models of hadrons and massive strings are discussed in detail. To correctly describe the dynamical aspects of the hadron-hadron interaction, especially of high-energy heavy-ion collisions, ideas from these models are proposed to be combined into a semiclassical unified string-flux tube model. Special emphasis is given to the dynamical string model recently developed on the basis of such a unified string-flux tube model.

We study two-dimensional U(N) and SU(N) gauge theories with a topological term on arbitrary surfaces. Starting from a lattice formulation we derive the continuum limit of the action which turns out to be a generalisation of the heat kernel in the presence of a topological term. In the continuum limit we can reconstruct the topological information encoded in the theta term. In the topologically trivial cases the theta term gives only a trivial shift to the ground state energy but in the topologically nontrivial ones it remains to be coupled to the dynamics in the continuum. In particular for the U(N) gauge group on orientable surfaces it gives rise to a phase transition at θ = π, similar to the ones observed in other models. Using the equivalence of 2d QCD and a 1d fermion gas on a circle we rewrite our result in the fermionic language and show that the theta term can be also interpreted as an external magnetic field imposed on the fermions.