Nonlinearly Realised Defect Symmetries and Anomalies

TL;DR

This paper investigates the nonlinear realization of defect symmetries and anomalies in conformal field theories, deriving universal identities and exploring scheme-independent quantities and new anomaly expressions.

Contribution

It provides a framework for understanding nonlinear defect symmetries, establishes universal integral identities, and uncovers new anomaly expressions in conformal defects.

Findings

Universal integral identities for defect correlation functions

Scheme-independent quantities for nonlinear symmetries

New expressions and discoveries of defect anomalies

Abstract

Conformal defects -- extended objects in conformal field theories -- carry localised excitations inherited from symmetry currents, known as the displacements and tilts. They capture the linear response of the defect to deformations of its shape or of its profile along internal symmetry directions. There is no universal formula for deformations beyond the linear order and this is subject to ambiguities of coordinate choices on coset spaces and scheme dependence in the quantum theory. We analyse the exact match between the two and identify the scheme independent quantities capturing nonlinearly realised symmetries. This leads to universal integral identities for correlation functions in the presence of tilts and displacements. We present several applications of them. We also study possible anomalies, recovering known ones, finding new expressions for them, and uncovering new ones.