Abstract
Initially introduced by A. Kitaev, topological K-theory plays a crucial role in the classification of free-fermion topological states. Building upon this foundation, D. Freed and G. W. Moore extended the concept to twisted equivariant K-theory, emphasizing the significance of twistings. These twistings can stem from various sources, such as antiunitary time reversal symmetries and charge-conjugate symmetries, resulting in the AZ ten classes. This presentation will focus on examining the momentum-space twistings that arise from real-space projective crystalline symmetries. Inspired by recent research on the nonsymmorphic structure of momentum space, we investigate a new type of twisting and explore its physical implications.
Anyone interested is welcome to attend.