BPS Skyrme models and contact geometry

TL;DR

This paper introduces a generalized Skyrme energy functional for maps between Riemannian and contact 3-manifolds, establishing topological bounds and analyzing solutions in specific geometric contexts.

Contribution

It extends the BPS Skyrme model to contact geometry and characterizes solutions via a new self-duality equation, providing insights into topological bounds and solution existence.

Findings

The energy functional admits a topological lower bound.

Strong Beltrami maps solve the self-duality equation.

No BPS solutions exist on $S^3$ with degree > 1 at lowest coupling.

Abstract

A Skyrme type energy functional for maps $\varphi$ from an oriented Riemannian 3-manifold $M$ to a contact 3-manifold $N$ is defined, generalizing the BPS Skyrme energy of Ferreira and Zakrzewski. This energy has a topological lower bound, attained by solutions of a first order self-duality equation which we call (strong) Beltrami maps. In the case where $N$ is the 3-sphere, we show that the original Ferreira-Zakrzewski model (which has $N=S^3$ with the standard contact structure) can have no BPS solutions on $M=S^3$ with $|\mathrm{deg}(\varphi)|>1$ if the coupling constant has the lowest admissible value.