Department of Physics, National University of Singapore

Upcoming Seminars

(Both online and in-person seminars will be broadcast via Zoom.)

(Click the upper right corner of this page to see the previous seminars and their recordings.)

Time: 9am, November 12 2024, GMT+8

Location: Online

Zoom: https://nus-sg.zoom.us/j/89860451618?pwd=lSouTW3ZYoabu24ltzdps9n5qhbKyu.1 

Password: 726763

Speaker: Arkya Chatterjee

Title: Quantized axial charge and the chiral anomaly in a Hamiltonian lattice model

Abstract: Realizing chiral global symmetries on a finite lattice is a long-standing challenge in lattice gauge theory, with potential implications for non-perturbative regularization of the Standard Model. One of the simplest examples of such a symmetry is the axial U(1) symmetry of the 1+1d massless Dirac fermion field theory: it acts by equal and opposite phase rotations on the left- and right-moving Weyl components of the Dirac field. This field theory also has a vector U(1) symmetry which acts identically on left- and right-movers. These two U(1) symmetries exhibit a mixed anomaly, commonly known as the Schwinger anomaly. In this talk, I will discuss how both symmetries are realized exactly in a "tight-binding" lattice Hamiltonian with a finite-dimensional Hilbert space. Intriguingly, the continuum anomaly of the abelian U(1) symmetries is matched on the lattice by a non-Abelian Lie algebra. The lattice symmetry forces the low-energy phase to be gapless, closely paralleling the effects of the anomaly in the continuum field theory.

The next seminar will be held at the beginning of the next semester.