<p>We study partition problems based on two ostensibly different kinds of energy functionals defined on <i>k</i>-partitions of metric graphs: Cheeger-type functionals whose minimisers are the <i>k</i>-Cheeger cuts of the graph, and the corresponding values are the <i>k</i>-Cheeger constants of the graph; and functionals built using the first eigenvalue of the Laplacian with positive, i.e., absorbing, Robin (delta) vertex conditions at the boundary of the partition elements. We prove existence of minimising <i>k</i>-partitions, <i>k</i> ≥ 2, for both these functionals. We also show that, for each <i>k</i> ≥ 2, as the Robin parameter <i>α</i> → 0, up to a renormalisation the spectral minimal Robin energy converges to the <i>k</i>-Cheeger constant. Moreover, up to a subsequence, the Robin spectral minimal <i>k</i>-partitions converge in a natural sense to a <i>k</i>-Cheeger cut of the graph. Finally, we show that as <i>α</i> → ∞ there is convergence in a similar sense to the corresponding Dirichlet minimal energy and partitions.</p><p>It is strongly expected that similar results hold on general (smooth, bounded) Euclidean domains and manifolds.</p>

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Cheeger cuts and Robin spectral minimal partitions of metric graphs

  • James B. Kennedy,
  • João P. Ribeiro

摘要

We study partition problems based on two ostensibly different kinds of energy functionals defined on k-partitions of metric graphs: Cheeger-type functionals whose minimisers are the k-Cheeger cuts of the graph, and the corresponding values are the k-Cheeger constants of the graph; and functionals built using the first eigenvalue of the Laplacian with positive, i.e., absorbing, Robin (delta) vertex conditions at the boundary of the partition elements. We prove existence of minimising k-partitions, k ≥ 2, for both these functionals. We also show that, for each k ≥ 2, as the Robin parameter α → 0, up to a renormalisation the spectral minimal Robin energy converges to the k-Cheeger constant. Moreover, up to a subsequence, the Robin spectral minimal k-partitions converge in a natural sense to a k-Cheeger cut of the graph. Finally, we show that as α → ∞ there is convergence in a similar sense to the corresponding Dirichlet minimal energy and partitions.

It is strongly expected that similar results hold on general (smooth, bounded) Euclidean domains and manifolds.