Quantization in the Presence of Gribov Ambiguities
  The non-perturbative validity of covariant BRST-quantization of gauge theories on compact Euclidean space-time manifolds is reviewed. BRST-quantization is related to the construction of a Topological Quantum Field Theory (TQFT) of Witten type on the gauge group. The criterion for the non-perturbative validity of the quantization is that the partition function of the corresponding TQFT does not vanish and that its (equivariant) BRST-algebra is free of anomalies. I sketch the construction of a TQFT whose partition function is proportional to the generalized Euler-characteristic of the coset space $SU(n)_{gauge}/SU(n)_{global}$ with an associated equivariant BRST-algebra that manifestly preserves translational symmetry. Some non-perturbative consequences of this approach are discussed. 
Martin Schaden (New York University)