Morse index, topology, and ends of minimal surfaces with noncompact free boundary
Abstract
We establish index estimates for complete two-sided free boundary minimal surfaces in smooth mean-convex domains of ℝ3 with noncompact boundary. We first prove 3Inds(Σ)≥ 2g+b−1, where g and b describe the conformal compactification. We then include all interior ends with their multiplicities, without further asymptotic assumptions, and selected boundary ends under an explicit condition ensuring vanishing cutoff errors. The proof combines a localized energy identity with a Riemann--Roch count on the conformal double. A boundary puncture at which the chosen forms are regular eliminates the exceptional space; if poles are allowed at every boundary puncture, this space has dimension at most one. We provide the mixed cutoff construction, examples distinguishing embedded boundary ends from reflected planar ends, and a separate analysis of the conformal Jacobi metric. The latter yields finite Dirichlet energy of the logarithmic conformal factor, but the unrestricted boundary-end estimate remains an open step. The compact-boundary case was treated by Cavalcante, Mendes, and dos Santos.
Related
- Topology, Morse Index, and Area of Minimal Surfaces in Three-Manifolds
- Index estimates for complete noncompact free boundary minimal surfaces
- The Morse index of prismatic free boundary minimal surfaces in the unit ball
- Rigidity and Morse index of free boundary minimal T-surfaces in the unit ball
- Topology and Dirichlet spectrum of free boundary minimal and CMC surfaces
BibTeX
@misc{batista2026morse,
title = {{Morse index, topology, and ends of minimal surfaces with noncompact free boundary}},
author = {Márcio Batista and Matheus B. Martins},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.29723},
eprint = {2609.29723},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.29723},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Morse index, topology, and ends of minimal surfaces with noncompact free boundary
AU - Márcio Batista
AU - Matheus B. Martins
PY - 2026
DA - 2026/09/24
PB - arXiv
DO - 10.48550/arxiv.2609.29723
UR - https://arxiv.org/abs/2609.29723
AB - We establish index estimates for complete two-sided free boundary minimal surfaces in smooth mean-convex domains of ℝ^3 with noncompact boundary. We first prove 3Ind_s(Σ)≥ 2g+b−1, where g and b describe the conformal compactification. We then include all interior ends with their multiplicities, without further asymptotic assumptions, and selected boundary ends under an explicit condition ensuring vanishing cutoff errors. The proof combines a localized energy identity with a Riemann--Roch count on the conformal double. A boundary puncture at which the chosen forms are regular eliminates the exceptional space; if poles are allowed at every boundary puncture, this space has dimension at most one. We provide the mixed cutoff construction, examples distinguishing embedded boundary ends from reflected planar ends, and a separate analysis of the conformal Jacobi metric. The latter yields finite Dirichlet energy of the logarithmic conformal factor, but the unrestricted boundary-end estimate remains an open step. The compact-boundary case was treated by Cavalcante, Mendes, and dos Santos.
ER -