Speaker: Dr. Geraint Evans (Academia Sinica)
Talk title: Anomalous coupling of vorticity, magnetic fields, and chemical potential to pions
Time: 2026/05/18 (Mon.) 12:30
Place: NCTS Physics 4F Lecture Hall, Cosmology Hall, NTU

Abstract: 
Over the past decade, much interest has been directed toward effects stemming from the chiral anomaly on matter under extreme conditions, e.g., in heavy-ion collisions and neutron stars. In chiral perturbation theory, such effects manifest from the Wess-Zumino-Witten (WZW) terms. Starting from a linear sigma model, I shall outline how to derive the WZW effective action in the presence of external vector, axial-vector, and pseudo-scalar fields using a derivative expansion of the fermionic determinant. From there, one can derive anomalous terms that couple vorticity, electromagnetic fields, and chemical potentials to pions. In particular, the vorticity is incorporated via a correspondence with the axial-vector field when one considers massless Dirac fermions. The anomalous terms include a part responsible for the so-called Chiral Soliton Lattice in QCD under large magnetic fields and a new term that couples the vorticity to charged pions. I will then briefly discuss the possible phenomenological implications of this new term.