Jon Chaika

  1. Diophantine properties of IETs and general systems: Quantitative proximality and connectivity.

    Authors: Jon Chaika, Michael Boshernitzan
    Subjects: Dynamical Systems
    Abstract

    We present shrinking targets results for general systems with the emphasis on
    applications for IETs (interval exchange transformations) $(J,T)$, $J=[0,1)$.
    In particular, we prove that if an IET $(J,T)$ is ergodic (relative to the
    Lebesgue measure $\lam$), then the equality \[ \liminf_{n\to\infty}\limits n
    |T^n(x)-y|=0 \tag{A1} \] holds for $\lam\ttimes\lam$-a. a. $(x,y)\in J^2$. The
    ergodicity assumption is essential: the result does not extend to all minimal
    IETs. The factor $n$ in (A1) is optimal (e. g., it cannot be replaced by $n
    \ln(\ln(\ln n))$.

  2. Borel-Cantelli sequences.

    Authors: Jon Chaika, Michael Boshernitzan
    Subjects: Dynamical Systems
    Abstract

    A sequence $\{x_{n}\}_1^\infty$ in $[0,1)$ is called Borel-Cantelli (BC) if
    for all non-increasing sequences of positive real numbers $\{a_n\}$ with
    $\underset{i=1}{\overset{\infty}{\sum}}a_i=\infty$ the set
    \[\underset{k=1}{\overset{\infty}{\cap}} \underset{n=k}{\overset{\infty}{\cup}}
    B(x_n, a_n))=\{x\in[0,1)\mid |x_n-x|<a_n \text{for} \infty
    \text{many}n\geq1\}\] has full Lebesgue measure. (To put it informally, BC
    sequences are sequences for which a natural converse to the Borel-Cantelli
    Theorem holds).

  3. There exists a topologically mixing IET.

    Authors: Jon Chaika
    Subjects: Dynamical Systems
    Abstract

    This paper uses a construction of M. Keane to show that there exists a
    topologically mixing interval exchange transformation.

  4. Shrinking targets for IETs: Extending a theorem of Kurzweil.

    Authors: Jon Chaika
    Subjects: Dynamical Systems
    Abstract

    This paper proves shrinking target results for IETs. Let {a_1\geq a_2
    \geq...} be a sequence of positive real numbers with divergent sum. Then for
    almost every IET T, the limsup of B(T^ix,a_i) has full Lebesgue measure (where
    B(z, e) is the open ball around z of radius e). Related results are established
    including the analogous result for geodesic flows on a translation surface.

  5. On the Frequency of Balanced Times in Cylinder Flows.

    Authors: David Ralston, Jon Chaika
    Subjects: Dynamical Systems
    Abstract

    Given an irrational alpha and an x in the unit interval, the set of balanced
    times, for which the same number of (k*alpha+x) (modulo one) are less than or
    equal to one half as are larger than one half, is in general infinite, but
    sparse in terms of density. We investigate the sparseness of this sequence in
    terms of summation over reciprocals. Our results are that for the generic pair
    (alpha,x), the resulting sum diverges, but there are certain exceptional alpha
    for which the associated sums converge for every x.

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