Spinodal Instability and Confinement *

The mechanism of quark confinement continues to be one of the stumbling block in particle physics and one tends to shelve it by the help of more or less ad hoc models motivated by QCD. Instead of a detailed construction of ”The Mechanism” which obviously involves some highly technical and non-perturbative issues of QCD we suggest in this talk a rather well known phenomenon, spinodal instability, as a natural ingredient of confinement. There are actually two mechanisms for quark confinement. One is established by means of studying Wilson-loops in quenched lattice QCD without dynamical quarks and is operating with a linearly rising potential between static fundamental color charges. One may call this hard mechanism because it is based on large energy scales to suppress localized quarks. Another mechanism, proposed by V. Gribov, is conjectured in QCD with dynamical, light quarks and is reminiscent of the supercritical vacuum in QED. The separation of a quark form a hadron triggers an increase in the running coupling constant which in turn generates screening by the antiquark of a q − q̄ vacuum-polarization. We may call this soft mechanism because the screening is achieved by vacuum fluctuations of the energy of a light meson. The soft mechanism is the real one, observed in hadrons and is based on the non-perturbative phenomena in the Dirac-see caused by the increase of the running coupling constant at large distances, the key