Please circulate! Quantum Matter in Mathematics and Physics (QMMP) 2023: https://cmsa.fas.harvard.edu/event_category/quantum-matter-seminar/ ----- This seminar will be in person! *Time: Nov 3rd, Fri 10-11:30 am ET* *Location: Harvard CMSA G10* Zoom: https://harvard.zoom.us/j/977347126 Password: cmsa ————————————————————————————————— Meng Cheng (Yale) Title: Symmetry and many-body topology in mixed states Abstract: It is by now well-understood that gapped ground states of local Hamiltonians can be classified topologically, and the nontrivial states exhibit many interesting topological phenomena. In this talk I’ll discuss recent developments in generalizing the topological classification to mixed states. Global symmetry plays a key role in understanding phases in pure states. For mixed states, certain “weak” symmetries may hold “on average” for the entire ensemble, in contrast to “strong" symmetries respected by each state in the ensemble. I will show that the interplay between these two kinds of symmetries lead to a rich landscape of symmetry-protected mixed states, and can also be used to characterize mixed state topological order. -------- Subscribe to Harvard CMSA Quantum Matter and other seminar videos (more to be uploaded): https://www.youtube.com/playlist?list=PL0NRmB0fnLJQAnYwkpt9PN2PBKx4rvdup Subscribe to Harvard CMSA seminar mailing list: https://forms.gle/1ewa7KeP6BxBuBeRA