The Adjunction Inequality for Weyl-Harmonic Maps

TL;DR

This paper extends the concept of minimal surfaces to Weyl-minimal surfaces within conformal manifolds with a Weyl connection, establishing a correspondence with holomorphic curves and proving an adjunction inequality for these surfaces.

Contribution

It introduces Weyl-minimal surfaces in conformal manifolds, establishes a correspondence with holomorphic curves, and proves an adjunction inequality for these surfaces in the almost-Hermitian setting.

Findings

Weyl-minimal surfaces correspond to holomorphic curves in twistor space.

The adjunction inequality relates Euler characteristics and Chern classes for Weyl-minimal surfaces.

Holomorphic curves satisfy the equality case of the adjunction inequality.

Abstract

In this paper we study an analog of minimal surfaces called Weyl-minimal surfaces in conformal manifolds with a Weyl connection $(M^4,c,D)$. We show that there is an Eells-Salamon type correspondence between nonvertical $\mathcal{J}$-holomorphic curves in the weightless twistor space and branched Weyl-minimal surfaces. When $(M,c,J)$ is conformally almost-Hermitian, there is a canonical Weyl connection. We show that for the canonical Weyl connection, branched Weyl-minimal surfaces satisfy the adjunction inequality \begin{equation}\label{adj} \chi(T_f\Sigma)+\chi(N_f\Sigma) \le \pm c_1(f^*T^{(1,0)}M). \end{equation} The $\pm J$-holomorphic curves are automatically Weyl-minimal and satisfy the corresponding equality.