BGD domains in p.c.f. self-similar sets II: spectral asymptotics for Laplacians

TL;DR

This paper derives detailed spectral asymptotics for Laplacians on p.c.f. self-similar sets with specific boundary structures, revealing explicit second terms in eigenvalue counting functions under certain homogeneity conditions.

Contribution

It provides explicit second-term asymptotics for eigenvalue counts of Laplacians on p.c.f. self-similar sets with graph-directed boundaries, extending Weyl's law with periodic oscillations.

Findings

Explicit second-term asymptotics for eigenvalue counting functions.

Identification of periodic oscillations in spectral asymptotics.

Connection between boundary structure and spectral behavior.

Abstract

Let $K$ be a p.c.f. self-similar set equipped with a strongly recurrent Dirichlet form. Under a homogeneity assumption, for an open set $\Omega\subset K$ whose boundary $\partial \Omega$ is a graph-directed self-similar set, we prove that the eigenvalue counting function $\rho^\Omega(x)$ of the Laplacian with Dirichlet or Neumann boundary conditions (Neumann only for connected $\Omega$) has an explicit second term as $x\to +\infty$, beyond the dominant Weyl term. If $\partial\Omega$ has a strong iterated structure, we establish that \begin{equation*} \rho^\Omega(x)=\nu(\Omega)G\Big(\frac{\log x}2\Big)x^{\frac{d_S}2}+\kappa(\partial\Omega)G_1\Big(\frac{\log x}2\Big)x^{\frac d2}+o\big(x^{\frac d2}\big), \end{equation*} where $G$ and $G_1$ are bounded periodic functions, $\nu$ and $\kappa$ are certain reference measures, and $d_S$ and $d$ are dimension-related parameters.