Partial Gauge Fixing and Equivariant Cohomology

Understand

Given a gauge theory with gauge group G, it is sometimes useful to find an equivalent formulation in terms of a non-trivial gauge subgroup H of G.

• This amounts to fixing the gauge partially from G down to H.
• We study this problem systematically, both from the algebraic and the path integral points of view.
• We find that the usual BRST cohomology must be replaced by an equivariant version and that the ghost Lagrangian must always include quartic ghost terms, even at tree level.