Min-max theory and existence of H-spheres with arbitrary codimensions

TL;DR

This paper proves the existence of branched immersed 2-spheres with prescribed mean curvature in certain Riemannian manifolds, establishing new results on their Morse index, curvature conditions, and homotopy classes, extending min-max theory.

Contribution

It introduces new existence results for H-spheres with arbitrary codimensions, under various curvature conditions, and addresses the homotopy problem for prescribed mean curvature surfaces.

Findings

Existence of H-spheres with prescribed mean curvature in manifolds with finite fundamental group.

Morse index lower bounds under isotropic curvature conditions.

Construction of 2-spheres with parallel mean curvature in positively curved manifolds.

Abstract

We demonstrate the existence of branched immersed 2-spheres with prescribed mean curvature, with controlled Morse index and with arbitrary codimensions in closed Riemannian manifold $N$ admitting finite fundamental group, where $\pi_k(N) \neq 0$ and $k \geq 2$, for certain generic choice of prescribed mean curvature vector. Moreover, we enhance this existence result to encompass all possible choices of prescribed mean curvatures under certain Ricci curvature condition on $N$ when $\dim{N} = 3$. When $\dim{N} \geq 4$, we establish a Morse index lower bound while $N$ satisfies some isotropic curvature condition. As a consequence, we can leverage latter strengthened result to construct 2-spheres with parallel mean curvature when $N$ has positive isotropic curvature and $\dim{N} \geq 4$. At last, we partially resolve the homotopy problem concerning the existence of a representative surface with prescribed mean curvature type vector field in some given homotopy classes.