arXiv subjects

Andrew Török

Publications and source records attributed to Andrew Török.

3 recordsLinked to original sources

arXiv2024

Birkhoff sum convergence of Fréchet observables to stable laws for Gibbs-Markov systems and applications

We use a Poisson point process approach to prove distributional convergence to a stable law for non square-integrable observables $ϕ: [0,1]\to R$, mostly of the form $ϕ(x) = d(x,x_0)^{-\frac{1}α}$,$0<α\le 2$, on Gibbs-Markov maps. A key result is to verify a standard mixing condition, which ensures that large values of the observable dominate the time-series, in the range $1<α\le 2$. Stable limit laws for observables on dynamical systems have been established in two settings: ``good observables'' (typically Hölder) on slowly mixing non-uniformly hyperbolic systems and ``bad'' observables (unbounded with fat tails) on fast mixing dynamical systems. As an application we investigate the interplay between these two effects in a class of intermittent-type maps.

math.DS↗

arXiv2024

Stable laws for random dynamical systems

In this paper we consider random dynamical systems formed by concatenating maps acting on the unit interval $[0,1]$ in an iid fashion. Considered as a stationary Markov process, the random dynamical system possesses a unique stationary measure $ν$. We consider a class of non square-integrable observables $ϕ$, mostly of form $ϕ(x)=d(x,x_0)^{-\frac{1}α}$ where $x_0$ is non-periodic point satisfying some other genericity conditions, and more generally regularly varying observables with index $α\in (0,2)$. The two types of maps we concatenate are a class of piecewise $C^2$ expanding maps, and a class of intermittent maps possessing an indifferent fixed point at the origin. Under conditions on the dynamics and $α$ we establish Poisson limit laws, convergence of scaled Birkhoff sums to a stable limit law and functional stable limit laws, in both the annealed and quenched case. The scaling constants for the limit laws for almost every quenched realization are the same as those of the annealed case and determined by $ν$. This is in contrast to the scalings in quenched central limit theorems where the centering constants depend in a critical way upon the realization and are not the same for almost every realization.

math.DS↗

arXiv2016

Central limit theorems for sequential and random intermittent dynamical systems

We establish self-norming central limit theorems for non-stationary time series arising as observations on sequential maps possessing an indifferent fixed point. These transformations are obtained by perturbing the slope in the Pomeau-Manneville map. We also obtain quenched central limit theorems for random compositions of these maps.

math.DS↗