Infinite-Order Lattice Anomalies and CPT

Salvatore Pace discusses the order of anomalies in global symmetries: the number of identical copies needed before their diagonal symmetry becomes anomaly-free. Familiar lattice examples often have finite order, whereas perturbative continuum anomalies have infinite order. The seminar examines Onsager symmetry as a lattice counterpart of chiral symmetry for a massless Dirac fermion in one spatial dimension. Its anomaly has order two, but imposing CPT symmetry on the lattice changes it to infinite order, bringing the lattice description closer to the continuum. The work was carried out with Elijah Lew-Smith and Shu-Heng Shao and is reported in arXiv:2606.12510. Attendance is at the IAS Bloomberg Lecture Hall; the organizer also offers Zoom access by request through the contact listed on the event page.