“Correlation functions and gauge-fixing beyond perturbation theory”
Correlation functions are very useful tools in the intermediate steps from the elementary degrees of freedom to observable physics. However, in gauge theories they depend on the chosen gauge. Beyond perturbation theory, the thus necessary fixing of the gauge becomes complicated due to the presence of the Gribov-Singer ambiguity.
The origins and properties of this ambiguity will be presented, with particular focus on the non-perturbative generalization of the Landau gauge. The consequences for methods and the gauge-dependent correlation functions will be detailed. Finally, the current challenges in a full formal resolution of the ambiguity will be outlined.