On nonlinear classical electrodynamics with an axionic term

TL;DR

This paper explores how axionic terms modify nonlinear electrodynamics, revealing that key axionic effects are universal and independent of the specific nonlinear Lagrangian form, with implications for topological insulators.

Contribution

It demonstrates that the main axionic effects in nonlinear electrodynamics are universal and determined solely by the axionic term, regardless of the nonlinear Lagrangian's specific form.

Findings

Major axionic effects are independent of the nonlinear Lagrangian type.

Universal features of axionic effects are fixed by the axionic term.

Insights applicable to topological insulators and related materials.

Abstract

Recently there has been a renewed interest in axionic generalization of electrodynamics due to its application to topological insulators. A low-energy electromagnetic response of these exotic materials was proposed to be described by an axionic term in the Lagrangian. Motivated by this it is of interest to study various aspects of axionic electrodynamics and analyze the universal features of the axionic effects. Here we discuss the axionic modification of generalized electrodynamics with a Lagrangian being an arbitrary function of two electromagnetic invariants. Surprisingly, the qualitative characteristics of the major axionic effects known in the Maxwell theory happen to be independent of the exact type of the nonlinear Lagrangian and are uniquely fixed by the form of the axionic term.