Tomáš Dohnal

  1. Localized Modes of the Linear Periodic Schr\"{o}dinger Operator with a Nonlocal Perturbation.

    Authors: Tomáš Dohnal, Michael Plum, Wolfgang Reichel
    Subjects: Spectral Theory
    Abstract

    We consider the existence of localized modes corresponding to eigenvalues of
    the periodic Schr\"{o}dinger operator $-\partial_x^2+ V(x)$ with an interface.
    The interface is modeled by a jump either in the value or the derivative of
    $V(x)$ and, in general, does not correspond to a localized perturbation of the
    perfectly periodic operator. The periodic potentials on each side of the
    interface can, moreover, be different. As we show, eigenvalues can only occur
    in spectral gaps.

  2. Perfectly Matched Layers for Coupled Nonlinear Schr\"{o}dinger Equations with Mixed Derivatives.

    Authors: Tomáš Dohnal
    Subjects: Numerical Analysis
    Abstract

    This paper constructs perfectly matched layers (PML) for a system of 2D
    Coupled Nonlinear Schr\"odinger equations with mixed derivatives which arises
    in the modeling of gap solitons in nonlinear periodic structures with a
    non-separable linear part. The PML construction is performed in Laplace Fourier
    space via a modal analysis and can be viewed as a complex change of variables.
    The mixed derivatives cause the presence of waves with opposite phase and group
    velocities, which has previously been shown to cause instability of layer
    equations in certain types of hyperbolic problems.

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