# Geometry and Laplacian on Discrete Magic Carpets

## TL;DR

This paper explores the geometry and spectral properties of infinite magic carpets, variants of the Sierpinski Carpet, using theoretical and numerical methods to analyze Laplacian spectra, differential equations, and random walk behavior.

## Contribution

It introduces new infinite fractal-like structures called infinite magic carpets and provides estimates, spectral approximations, and evidence for their analysis.

## Key findings

- Size estimates for metric balls are nearly optimal.
- Numerical spectra of the graph Laplacian are obtained.
- Evidence suggests the random walk is transient and the spectrum is continuous.

## Abstract

We study several variants of the classical Sierpinski Carpet (SC) fractal. The main examples we call infinite magic carpets (IMC), obtained by taking an infinite blowup of a discrete graph approximation to SC and identifying edges using torus, Klein bottle or projective plane type identifications. We use both theoretical and experimental methods. We prove estimates for the size of metric balls that are close to optimal. We obtain numerical approximations to the spectrum of the graph Laplacian on IMC and to solutions of the associated differential equations: Laplace equation, heat equation and wave equation. We present evidence that the random walk on IMC is transient, and that the full spectral resolution of the Laplacian on IMC involves only continuous spectrum. This paper is a contribution to a general program of eliminating unwanted boundaries in the theory of analysis on fractals.