the story is about 3d mirror symmetry.

from a 3d N=4 SYM theory, you have Coulomb branch and Higgs branch as low energy effective field theory.

Consider boundary conditions. If we did A-twist in the bulk, we have A-twist in the boundary. 2d A-model with a target space that has a G-action.

Do we consider a sandwich, where on the left boundary, we have Dirichlet BC, and right boundary we have Neumann condition? (What does these mean?)

Or do we consider an interface: a theory and a dual theory share a common wall?