HTL quasiparticle picture of the thermodynamics of QCD

Starting from a nonperturbative expression for entropy and density obtained from $\Phi$-derivable two-loop approximations to the thermodynamic potential, a quasiparticle model for the thermodynamics of QCD can be developed which incorporates the physics of hard thermal loops and leads to a reorganization of the otherwise ill-behaved thermal perturbation theory through order $\alpha_s^{3/2}$. Some details of this reorganization are discussed and the differences to simpler quasiparticle models highlighted. A comparison with available lattice data shows remarkable agreement down to temperatures of $\sim 2.5 T_c$.Comment: Talk given at the International Conference on Statistical QCD, Bielefeld, Germany, August 26--30, 2001. 10 pages LATEX, 7 figure

HTL-resummed thermodynamics of hot and dense QCD: An update

We review the proposal to resum the physics of hard thermal loops in the thermodynamics of the quark-gluon plasma through nonperturbative expressions for entropy and density obtained from a Phi-derivable two-loop approximation. A comparison with the recently solved large-N_f limit of hot QCD is performed, and some updates, in particular on quark number susceptibilities, are made.Comment: 10 pages, 6 figures. To appear in the proceedings of Strong and Electroweak Matter (SEWM 2002), Heidelberg, Germany, 2-5 Oct 2002. v2: 1 typo and 2 references update

A new anomalous contribution to the central charge of the N=2 monopole

We calculate the one-loop corrections to the mass and central charge of the BPS monopole in N=2 super-Yang-Mills theory in 3+1 dimensions using a supersymmetry-preserving version of dimensional regularization adapted to solitons. In the renormalization scheme where previous studies have indicated vanishing quantum corrections, we find nontrivial corrections that we identify as the 3+1 dimensional analogue of the anomaly in the conformal central charge of the N=1 supersymmetric kink in 1+1 dimensions. As in the latter case, the associated contribution to the ordinary central charge has exactly the required magnitude to preserve BPS saturation at the one-loop level. It also restores consistency of calculations involving sums over zero-point energies with the low-energy effective action of Seiberg and Witten.Comment: 1+10 pages. v3: version to appear in Physics Letters B (more precise title and abstract, additional explanations in the text concerning the nature of the anomaly involved