Hello, I'm interested in (typically topological) QFTs arising from Lagrangians which are pure constraint, ie. of the form f(ψ) λ, where λ is a Lagrange multiplier field not appearing in f(ψ). Perturbatively, the partition function merely counts the solutions of f(ψ)=0. What about nonperturbatively? I imagine there might be situations where exponentially suppressed tunneling phenomena affect the partition function. I am imagining something like the kinks for the particle on a space with a Morse potential. How can I figure out if this is the case? What about boundary conditions for these theories? Has anyone considered these? Thanks.