Causal Structure and Birefringence in Nonlinear Electrodynamics

TL;DR

This paper explores the causal structure of nonlinear electrodynamics, identifying conditions for effective metrics and proving the uniqueness of birefringence-free models.

Contribution

It characterizes the effective metric in nonlinear electrodynamics and proves the uniqueness of the birefringence-free analytic Lagrangian.

Findings

Certain Lagrangians produce an effective metric conformal to Minkowski

Only one analytic nonlinear electrodynamics model exhibits no birefringence

The causal structure depends on the form of the Lagrangian

Abstract

We investigate the causal structure of general nonlinear electrodynamics and determine which Lagrangians generate an effective metric conformal to Minkowski. We also proof that there is only one analytic nonlinear electrodynamics presenting no birefringence.