David Borthwick

  1. Sharp geometric upper bounds on resonances for surfaces with hyperbolic ends.

    Authors: David Borthwick
    Subjects: Spectral Theory
    Abstract

    We establish a sharp geometric constant for the upper bound on the resonance
    counting function for surfaces with hyperbolic ends. An arbitrary metric is
    allowed within some compact core, and the ends may be of hyperbolic planar,
    funnel, or cusp type. The constant in the upper bound depends only on the
    volume of the core and the length parameters associated to the funnel or
    hyperbolic planar ends.

  2. Sharp upper bounds on resonances for perturbations of hyperbolic space.

    Authors: David Borthwick
    Subjects: Spectral Theory
    Abstract

    For certain compactly supported metric and/or potential perturbations of the
    Laplacian on $\mathbb{H}^{n+1}$, we establish an upper bound on the resonance
    counting function with an explicit constant that depends only on the dimension,
    the radius of the unperturbed region in $\mathbb{H}^{n+1}$, and the volume of
    the metric perturbation. This constant is shown to be sharp in the case of
    scattering by a spherical obstacle.

  3. Sharp upper bounds on resonances for perturbations of hyperbolic space.

    Authors: David Borthwick
    Subjects: Spectral Theory
    Abstract

    For certain compactly supported metric and/or potential perturbations of the
    Laplacian on $\mathbb{H}^{n+1}$, we establish an upper bound on the resonance
    counting function with an explicit constant that depends only on the dimension,
    the radius of the unperturbed region in $\mathbb{H}^{n+1}$, and the volume of
    the metric perturbation. This constant is shown to be sharp in the case of
    scattering by a spherical obstacle.

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