Nonperturbative applications of the world-line formalism
Université de Heidelberg
Wed, Dec. 06th 2006, 14:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
Various models, where the information on the nonperturbative properties of QCD can be obtained by using the world-line formalism, will be considered. In the quenched case, a random-walk-type model of the string passing through heavy valence gluons yields a correct estimate of the deconfinement temperature and a critical behavior of the string tension. In the unquenched case, the corresponding entropy and internal energy of the static quark-antiquark pair are in a good qualitative agreement with the lattice results. Also in the unquenched case, we present a model of string breaking, based on the production of quark-antiquark pairs in the field of the chromoelectric flux tube. We predict the form of the static quark-antiquark potential and evaluate the string-breaking length at zero temperature and at temperatures close to the deconfining one. We further discuss the various Ansaetze for the minimal area of the Wilson loop, which allow for an analytic calculation of the corresponding path integral. One of those is applied to the calculation of the heavy-quark condensates in the dual superconductor and the stochastic models of the QCD vacuum. Another one is used for the derivation of the so-called freezing of the running QCD coupling in the infra-red region.