Bose-Einstein correlations in thermal field theory

Two-particle correlation functions are calculated for bosons emitted from a localized thermal source (the ``glow'' of a ``hot spot''). In contrast to existing work, non-equilibrium effects up to first order in gradients of the particle distribution function are taken into account. The spectral width of the bosons is shown to be an important quantity: If it is too small, they do not equilibrate locally and therefore strongly increase the measured correlation radius. In memoriam of Eugene Wigner and Hiroomi Umezawa.