  Spectral sums of the Dirac-Wilson operator and their relation to the Polyakov
loop are thoroughly investigated. The approach by Gattringer is generalized to
mode sums which reconstruct the Polyakov loop locally. This opens the
possibility to study the mode sum approximation to the Polyakov loop
correlator. The approach is re-derived for the ab initio continuum formulation
of Yang-Mills theories, and the convergence of the mode sum is studied in
detail. The mode sums are then explicitly calculated for the Schwinger model
and SU(2) gauge theory in a homogeneous background field. Using SU(2) lattice
gauge theory, the IR dominated mode sums are considered and the mode sum
approximation to the static quark anti-quark potential is obtained numerically.
We find a good agreement between the mode sum approximation and the static
potential at large distances for the confinement and the high temperature
plasma phase.
