Character Formulas for Kirillov-Reshetikhin Modules via Folding of Supercharacters of $\mathfrak{g}\mathfrak{l}(M\mathrm{\mid }N)$

We derive decomposition formulas for supercharacters of quantum affine ortho-symplectic superalgebras and twisted quantum affine superalgebras into supercharacters of their finite-type quantum sub-superalgebras, by employing Cauchy-type identities for supersymmetric Schur functions. These formulas are obtained via a folding (reduction) procedure applied to the supercharacters of the finite-dimensional general linear Lie superalgebra $\mathfrak{g}\mathfrak{l}(M\mathrm{\mid }N)$. As a special case, our results provide explicit character formulas for a class of Kirillov–Reshetikhin modules of quantum affine algebras (and their Yangian counterparts), thereby proving a previously proposed conjecture derived from Bethe ansatz analysis (arXiv:2309.16660).