Half-BPS Boundaries and the RG-Wall of $\mathcal{N}=2$ $SU(N)$ SYM

We identify the 3d theory that realizes the RG-wall interface of 4d $\mathcal{N}=2$ $SU(N)$ Super-Yang-Mills, interpolating between the UV Lagrangian and the IR Seiberg-Witten effective description. The same theory also describes the low-energy boundary condition that corresponds to giving half-BPS Dirichlet boundary condition in the Lagrangian description of 4d $\mathcal{N}=2$ $SU(N)$ SYM. The theory is a 3d $\mathcal{N}=2$ SCFT that can be obtained as a massive deformation of the $T[SU(N)]$ theory, which is the S-duality interface of 4d $\mathcal{N}=4$ $SU(N)$ SYM. As the main validating tests, we match half-indices and discuss non-trivial consistency conditions when colliding such interfaces.