Potential theory Potential theory on fractals and metric spaces Theorem
Kigami's construction of Laplacians on post-critically finite fractals
Builds on Iterated function systemLaplacian matrixResistance formDirichlet form
Statement
Let be the attractor of an iterated function system of contracting similitudes , and assume that is connected and post-critically finite. Let be its finite boundary set, let , and for a word write and . Let be the energy of an electrical network on with conductances that connect , and let . For set Assume the renormalization condition: for every , the minimum of over all with equals . Then:
- For every function , the sequence is nondecreasing in ; let be its limit in .
- Let , and define from by polarization. Then is a resistance form on , and its resistance metric induces the usual topology of .
- For every finite Borel measure on whose support is , is a local regular Dirichlet form on .
- The Laplacian is defined by: , with and continuous, if for every that vanishes on .
Remarks
The renormalization condition says that is the trace of on , and by self-similarity is then the trace of on for every . This gives the monotonicity in clause 1 and shows that each on has a unique extension to with the same energy, the harmonic extension. The bound with a resistance that is small on small cells gives the continuity of functions of finite energy; this uses . For the Sierpiński gasket, with the unit-conductance triangle and all , the renormalization condition is the computation of the "– rule", as in Laplacian on the Sierpiński gasket. Finding and that satisfy the renormalization condition is a nonlinear fixed-point problem, and the theorem takes a solution as given. A pair that satisfies the renormalization condition is called a harmonic structure, and it is called regular when all . The construction is due to Kigami.
Going deeper
For a student
The result turns the analysis of a fractal into linear algebra on a sequence of finite graphs, each step governed by the same Laplacian matrix. Harmonic functions are determined by their values on and are computed level by level through fixed harmonic extension matrices. Once the Laplacian exists, one studies its spectrum, the heat equation and its heat kernel, and the diffusion process attached to the Dirichlet form by the Fukushima correspondence. The resistance metric is the natural metric for these estimates. The approach complements the probabilistic one, in which Brownian motion on the gasket is built as a limit of random walks on the graphs .
Reading path
To understand this page from the ground up, read these 5 pages in order. The foundations come first.
Show the path as a graph
- no evidence level
- Dirichlet form concept
- Iterated function system concept
- Laplacian matrix concept
- Resistance form concept
- Kigami's construction of Laplacians on post-critically finite fractals statement
Further reading
About this page
| Tag | VXB4G47Z3T |
|---|---|
| URI | m2://VXB4G47Z3T |
| Kind | statement, theorem |
| Writing | W0 stub |
| MSC | 31E05, 28A80, 31C25 |
| Status | This copy of the site has no build data. Run m2 status VXB4G47Z3T. |
| About | Analysis on fractals, Resistance form |
| Uses | Iterated function system, Laplacian matrix, Resistance form, Dirichlet form |
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