Gauge-invariant two-point correlator of energy density in deconfining   SU(2) Yang-Mills thermodynamics
  The thesis is considering aspects of SU(2) Yang-Mills thermodynamics in its deconfining high-temperature phase. We calculate the two-point correlation function of the energy density of the photon in a thermalized gas, at first in the conventional U(1) gauge theory, followed by a calculation, where the photon is identified with the massless gauge mode in deconfining SU(2) Yang-Mills thermodynamics. Apart from the fact, that this calculation is interesting from a technical point of view, we can consider several aspects of phenomenological relevance. Since we interpret the two-point correlator of energy density as a measure for the energy transfer, and thus for the electromagnetic interaction of microscopic objects, such as atoms immersed into a photon gas, we are able to give an explanation for the unexpected stability of cold, innergalactic clouds consisting of atomic hydrogen.   Subsequently, we evaluate the spatial string tension in deconfining SU(2) Yang-Mills thermodynamics, which can be regarded as measure for the magnetic flux through the area enclosed by the associated Wilson loop. On the level of on-shell polarization effects for the massless mode we observe a perimeter-law, and we speculate that the lattice-obtained area-law is induced by off-shell contributions to the polarization tensor. Moreover, we discuss an interesting two-loop result for the pressure which seems to be associated with the presence of screened magnetic monopoles being responsible for an area-law. 
Jochen Keller