K-theoretic Global Symmetry in String-constructed QFT and T-duality

We propose that generalized symmetries in some string-constructed QFTs are given by twisted K-theory, so as to be manifestly consistent under T-duality. We thus have even-form and odd-form symmetries determined by K^*N(∂ X), the twisted K-theory as D-brane charges on the asymptotic boundary ∂ X of internal geometry X with twist class N. For these QFTs, "p-form symmetries" are no longer separately well-defined for individual p, but instead mixed up. We discuss 6D ADE-type (2,0) SCFTs and some 6d (1,0) LSTs as examples, and demonstrate their twisted K-theoretic symmetries to be consistent with T-duality.