Walter Bergweiler

  1. On the packing dimension of the Julia set and the escaping set of an entire function.

    Authors: Walter Bergweiler
    Subjects: Complex Variables
    Abstract

    We show that for large classes of entire functions the Julia set and the
    escaping set have packing dimension two. For example, this is the case for
    entire functions which are bounded on a curve tending to infinity. More
    generally, we show that the result holds under suitable growth conditions
    involving the minimum and maximum modulus.

  2. Dynamics of a higher dimensional analog of the trigonometric functions.

    Authors: Walter Bergweiler, Alexandre Eremenko
    Subjects: Dynamical Systems
    Abstract

    We introduce a higher dimensional quasiregular map analogous to the
    trigonometric functions and we use the dynamics of this map to define, for d>1,
    a partition of d-dimensional Euclidean space into curves tending to infinity
    such that two curves may intersect only in their endpoints and such that the
    union of the curves without their endpoints has Hausdorff dimension one.

  3. Normal families and fixed points of iterates.

    Authors: Walter Bergweiler
    Subjects: Complex Variables
    Abstract

    Let F be a family of holomorphic functions and let K be a constant less than
    4. Suppose that for all f in F the second iterate of f does not have fixed
    points for which the modulus of the multiplier is greater than K. We show that
    then F is normal. This is deduced from a result about the multipliers of
    iterated polynomials.

  4. On the Hausdorff dimension of the Julia set of a regularly growing entire function.

    Authors: Walter Bergweiler, Bogusława Karpińska
    Subjects: Dynamical Systems
    Abstract

    We show that if the growth of a transcendental entire function f is
    sufficiently regular, then the Julia set and the escaping set of f have
    Hausdorff dimension 2.

  5. On the Hausdorff dimension of the Julia set of a regularly growing entire function.

    Authors: Walter Bergweiler, Bogusława Karpińska
    Subjects: Dynamical Systems
    Abstract

    We show that if the growth of a transcendental entire function f is
    sufficiently regular, then the Julia set and the escaping set of f have
    Hausdorff dimension 2.

  6. On the number of solutions of a transcendental equation arising in the theory of gravitational lensing.

    Authors: Walter Bergweiler, Alexandre Eremenko
    Subjects: Complex Variables
    Abstract

    The equation in the title describes the number of bright images of a point
    source under lensing by an elliptic object with isothermal density. We prove
    that this equation has at most 6 solutions. Any number of solutions from 1 to 6
    can actually occur.

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