[NTU String Seminar] Chiral anomalies and CPT

• Event Date: 2026-01-02
• Chen, Jhan Yu 陳詹喻
• High Energy Physics and Astrophysics High energy theory
• Speaker: Shu-Heng Shao (MIT)  /  Host: Prof. Pei-Ming Ho
  Place: Rm. 815, Dept. of Physics, NTU

Title: [NTU String Seminar] Chiral anomalies and CPT
Speaker: Shu-Heng Shao (MIT) 
Time: 2026/1/2 (Fri.) 14:30
Place: Rm. 815, Dept. of Physics, NTU
 

Abstract

We discuss how the vector and axial U(1) symmetries of a massless Dirac fermion in 1+1d are realized in Hamiltonian lattice systems. Interestingly, these two lattice charges do not commute and form a non-abelian algebra, first discussed by Onsager. We prove that these symmetries force the low-energy phase to be gapless, reminiscent of consequences from perturbative anomalies of continuous global symmetries in quantum field theory. This lattice anomaly is of order 2, but when a lattice CPT symmetry is further imposed, the anomaly becomes of infinite order (i.e., torsion-free).