Anomalies and phases of strongly-coupled chiral gauge theories: recent developments

TL;DR

Recent advances in understanding strongly-coupled chiral gauge theories involve new concepts like generalized symmetries and anomalies, providing clearer insights into their phases and dynamics, contrasting with traditional QCD approaches.

Contribution

The paper reviews recent developments applying generalized symmetries and anomalies to chiral gauge theories, offering new perspectives on their phase structure and dynamics.

Findings

Generalized anomalies favor the dynamical Higgs phase over confining vacua.

New techniques clarify the phase structure of chiral gauge theories.

Analogies between QCD and chiral gauge theories are explored.

Abstract

After many years of investigations, our understanding of the dynamics of strongly-coupled chiral gauge theories is still quite unsatisfactory today. Conventional wisdom about strongly-coupled gauge theories, successfully applied to QCD, is not always as useful in chiral gauge theories. Recently some new ideas and techniques have been developed, which involve concepts of generalized symmetries, of gauging a discrete center symmetry, and of generalizing the 't Hooft anomaly matching constraints to include certain mixed symmetries. This new development has been applied to chiral gauge theories, leading to many interesting, sometimes quite unexpected, results. For instance, in the context of generalized Bars-Yankielowicz and generalized Georgi-Glashow models, these new types of anomalies give a rather clear indication in favor of the dynamical Higgs phase, against confining, flavor symmetric vacua. Another closely related topics is strong anomaly and the effective low-energy action representing it. It turns out that they have significant implications on the phase of chiral gauge theories, giving indications consistent with the findings based on the generalized anomalies. Some striking analogies and contrasts between the massless QCD and chiral gauge theories seem to emerge from these discussions. The aim of this work is to review these developments.