Alina Ostafe

  1. Degree Growth, Linear Independence and Periods of a Class of Rational Dynamical Systems.

    Authors: Alina Ostafe, Igor Shparlinski
    Subjects: Number Theory
    Abstract

    We introduce and study algebraic dynamical systems generated by triangular
    systems of rational functions. We obtain several results about the degree
    growth and linear independence of iterates as well as about possible lengths of
    trajectories generated by such dynamical systems over finite fields. Some of
    these results are generalisations of those known in the polynomial case, some
    are new even in this case.

  2. Pseudorandomness and Dynamics of Fermat Quotients.

    Authors: Alina Ostafe, Igor Shparlinski
    Subjects: Number Theory
    Abstract

    We obtain some theoretic and experimental results concerning various
    properties (the number of fixed points, image distribution, cycle lengths) of
    the dynamical system naturally associated with Fermat quotients acting on the
    set $\{0, ..., p-1\}$. We also consider pseudorandom properties of Fermat
    quotients such as joint distribution and linear complexity.

  3. On the Length of Critical Orbits of Stable Quadratic Polynomials.

    Authors: Igor E. Shparlinski, Alina Ostafe
    Subjects: Number Theory
    Abstract

    We use bounds of multiplicative character sums together with some recent
    results of N. Boston and R. Jones, to show that the critical orbit of quadratic
    polynomials over a finite field of $q$ elements is of length $O(q^{3/4})$,
    improving upon the trivial bound $q$.

  4. On the Length of Critical Orbits of Stable Quadratic Polynomials.

    Authors: Igor E. Shparlinski, Alina Ostafe
    Subjects: Number Theory
    Abstract

    We use bounds of multiplicative character sums together with some recent
    results of N. Boston and R. Jones, to show that the critical orbit of quadratic
    polynomials over a finite field of $q$ elements is of length $O(q^{3/4})$,
    improving upon the trivial bound $q$.

  5. Pseudorandom Numbers and Hash Functions from Iterations of Multivariate Polynomials.

    Authors: Igor E. Shparlinski, Alina Ostafe
    Subjects: Number Theory
    Abstract

    Dynamical systems generated by iterations of multivariate polynomials with
    slow degree growth have proved to admit good estimates of exponential sums
    along their orbits which in turn lead to rather stronger bounds on the
    discrepancy for pseudorandom vectors generated by these iterations. Here we add
    new arguments to our original approach and also extend some of our recent
    constructions and results to more general orbits of polynomial iterations which
    may involve distinct polynomials as well.

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