Alexander Teplyaev

  1. Spectral Analysis and Dirichlet Forms on Barlow-Evans Fractals.

    Authors: Alexander Teplyaev, Benjamin Steinhurst
    Subjects: Classical Analysis and ODEs
    Abstract

    We show that if a Barlow-Evans Markov process on a vermiculated space is
    symmetric, then one can study the spectral properties of the corresponding
    Laplacian using projective limits. For some examples, such as the Laakso spaces
    and a Spierpinski P\^ate \`a Choux, one can develop a complete spectral theory,
    including the eigenfunction expansions that are analogous to Fourier series.
    Also, one can construct connected fractal spaces isospectral to the fractal
    strings of Lapidus and van Frankenhuijsen.

  2. Random walks on barycentric subdivisions and the Strichartz hexacarpet.

    Authors: Alexander Teplyaev, Matthew Begue, Daniel J. Kelleher, Aaron Nelson, Hugo Panzo, Ryan Pellico
    Subjects: Metric Geometry
    Abstract

    We investigate the relation between simple random walks on repeated
    barycentric subdivisions of a triangle and a self-similar fractal, Strichartz
    hexacarpet, which we introduce. We explore a graph approximation to the
    hexacarpet in order to establish a graph isomorphism between the hexacarpet
    approximations and Barycentric subdivisions of the triangle, and discuss
    various numerical calculations performed on the these graphs. We prove that
    equilateral barycentric subdivisions converge to a self-similar geodesic metric
    space of dimension log(6)/log(2), or about 2.58.

  3. Derivations and Dirichlet forms on fractals.

    Authors: Alexander Teplyaev, Marius Ionescu, Luke G. Rogers
    Subjects: Operator Algebras
    Abstract

    We study derivations and Fredholm modules on metric spaces with a local
    regular conservative Dirichlet form. In particular, on finitely ramified
    fractals, we show that there is a non-trivial Fredholm module if and only if
    the fractal is not a tree (i.e. not simply connected). This result relates
    Fredholm modules and topology, and refines and improves known results on p.c.f.
    fractals.

  4. Spectral analysis on infinite Sierpinski fractafolds.

    Authors: Alexander Teplyaev, Robert Strichartz
    Subjects: Functional Analysis
    Abstract

    A fractafold, a space that is locally modeled on a specified fractal, is the
    fractal equivalent of a manifold. For compact fractafolds based on the
    Sierpinski gasket, it was shown by the first author how to compute the discrete
    spectrum of the Laplacian in terms of the spectrum of a finite graph Laplacian.
    A similar problem was solved by the second author for the case of infinite
    blowups of a Sierpinski gasket, where spectrum is pure point of infinite
    multiplicity. Both works used the method of spectral decimations to obtain
    explicit description of the eigenvalues and eigenfunctions.

  5. Smooth bumps, a Borel theorem and partitions of smooth functions on p.c.f. fractals.

    Authors: Robert S. Strichartz, Luke G Rogers, Alexander Teplyaev
    Subjects: Classical Analysis and ODEs
    Abstract

    We provide two methods for constructing smooth bump functions and for
    smoothly cutting off smooth functions on fractals, one using a probabilistic
    approach and sub-Gaussian estimates for the heat operator, and the other using
    the analytic theory for p.c.f. fractals and a fixed point argument. The heat
    semigroup (probabilistic) method is applicable to a more general class of
    metric measure spaces with Laplacian, including certain infinitely ramified
    fractals, however the cut off technique involves some loss in smoothness. From
    the analytic approach we establish a Borel theorem for p.c.f.

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