Anomalous symmetry breaking and its macroscopic manifestations

by Andrey Sadofyev (Massachusetts Inst. of Technology (US))

Thursday 29 Jan 2026, 10:00 → 12:00 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

The triangle diagram corresponding to the axial anomaly in the theory of massless (gapless) fermions exhibits a non-trivial large distance/infrared behavior, modifying the low-energy limit of the theory. In many-body systems, the anomaly may be manifested at the macroscopic level by novel transport phenomena, often referred to as chiral effects. The anomaly is quantum in its nature and so are the chiral effects, being similar in this sense to such phenomena as superfluidity and superconductivity. This anomalous transport has attracted significant attention in the literature, appearing in a variety of systems from novel materials with ultrarelativistic spectrum to quark-gluon plasma. Moreover, the anomaly may lead to a partial bosonization in systems of massless fermions, resulting in a new collective pseudoscalar mode -- a collective or synthetic axion. Fundamental axions and axion-like particles are often discussed in the context of high-energy physics as potential solutions for the strong charge-parity problem, appearing in the fundamental theory of strong interactions, and are also being actively searched for as Dark Matter candidates. In this talk, I will briefly review the many-body anomalous dynamics, and discuss how collective axionic modes may be realized in condensed matter systems such as Weyl semimetals.