Deformed Hopfion-Ra\~nada Knots in ModMax Electrodynamics

TL;DR

This paper investigates how null electromagnetic knots, specifically hopfion-Rada configurations, are affected within ModMax nonlinear electrodynamics, revealing a continuous family of deformed solutions that revert to the original knots when nonlinear effects vanish.

Contribution

It identifies a new class of deformed hopfion-Rada knots in ModMax theories, extending the understanding of topological solutions in nonlinear electrodynamics.

Findings

Deformed hopfion-Rada knots form a continuous class in ModMax theories.

These solutions revert to original knots when the nonlinear parameter is zero.

Null field configurations are singular in nonlinear electrodynamics, but specific deformations are possible.

Abstract

Source-free so-called ModMax theories of nonlinear electrodynamics in the four dimensional Minkowski spacetime vacuum are the only possible continuous deformations -- and as a function of a single real and positive parameter -- of source-free Maxwell linear electrodynamics in the same vacuum, which preserve all the same Poincar\'e and conformal spacetime symmetries as well as the continuous duality invariance of Maxwell's theory. Null field configurations of the latter however, including null electromagnetic knots, are singular for the Lagrangian formulation of any spacetime Poincar\'e and conformal invariant theory of nonlinear electrodynamics. In particular null hopfion-Ra\~nada knots are a distinguished and fascinating class on their own of topologically nontrivial solutions to Maxwell's equations. This work addresses the fate of these configurations within ModMax theories. A doubled class of ModMax deformed hopfion-Ra\~nada knots is thereby identified, each of which coalescing back in a continuous fashion to the original hopfion-Ra\~nada knot when the nonlinear deformation parameter is turned off.