PUB - Publikationen an der Universität Bielefeld

The deconfined phase in finite temperature SU(2) gauge theory shows clear interaction effects in the temperature range 1 less-than-or-equal-to T/T(c) less-than-or-equal-to 2. The interaction measure DELTA = (epsilon - 3 P)T4, defined in terms of the energy density epsilon and the pressure P, peaks at some temperature T above the critical temperature T(c) and is different from zero in the entire temperature interval mentioned. High statistics lattice calculations provide numerical results for the pressure P and the entropy density s = (epsilon + P)/T. We interpret these results in terms of an ideal gas of quasi-gluons propagating in a refractive medium. The refractive properties of the medium are parametrized in terms of a temperature-dependent effective mass M(T) of the excitations, which is determined from the lattice data. It shows a quite non-trivial behaviour: M(T) decreases from T = T(c) until T congruent-to 2 T(c); beyond this point it starts increasing again, and at high temperatures it approaches the perturbative thermal mass M(T) approximately gT.