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Dalia Terhesiu

Publications and source records attributed to Dalia Terhesiu.

At least 19 recordsLinked to original sources
arXiv2026

On multidimensional infinite dihedral group extensions of Gibbs Markov maps

We obtain a local central limit theorem for cocycles associated with a class of non abelian and non compact group extensions of Gibbs Markov maps. This class consists of multidimensional infinite dihedral groups. Unlike in the set up of the random walks on groups, we cannot use the convolution of measures on the group and instead we resort to an approach based on irreducible representations. Depending on the dimension of the group, we obtain either mixing, and thus ergodicity, or dissipativity. Also, we obtain the asymptotics of the first return time of the group extension to the origin.

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arXiv2025

On some random billiards in a tube with superdiffusion

We consider a class of random billiards in a tube, where reflection angles at collisions with the boundary of the tube are random variables rather than deterministic (and elastic) quantities. We obtain a (non-standard) Central Limit Theorem for the horizontal displacement of a particle, which marginally fails to have a second moment w.r.t.\ the invariant measure of the random billiard.

math.DS↗
arXiv2025

Ratio limits and pressure function for group extensions of Gibbs Markov maps

Ratio limit theorems for random walks on (various) groups are known. We obtain a generalization of this type of ratio limit for deterministic walks on certain groups driven by Gibbs Markov maps. In terms of proofs, the main difficulty comes down to the absence of a convolution structure. Also, for (finitely generated) group extensions of Gibbs Markov maps we obtain a characterization of the pressure function without a symmetry assumption.

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arXiv2025

On asymptotic expansions of ergodic integrals for $\Z^d$-extensions of translation flows

We obtain expansions of ergodic integrals for $\Z^d$-covers of compact self-similar translation flows, and as a consequence we obtain a form of weak rational ergodicity with optimal rates. As examples, we consider the so-called self-similar $(s,1)$-staircase flows ($\Z$-extensions of self-similar translations flows of genus-$2$ surfaces), and particular cases of the Ehrenfest wind-tree model.

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arXiv2024

Hölder continuity of measures for heavy tail potentials

For a class of potentials $ψ$ satisfying a condition depending on the roof function of a suspension (semi)flow, we show an EKP inequality, which can be interpreted as a Hölder continuity property in the weak${^*}$ norm of measures, with respect to the pressure of those measures, where the Hölder exponent depends on the $L^q$-space that $ψ$ belongs to. This also captures a new type of phase transition for intermittent (semi)flows (and maps).

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arXiv2024

Strong mixing for the periodic Lorentz gas flow with infinite horizon

We establish strong mixing for the $\mathbb Z^d$-periodic, infinite horizon, Lorentz gas flow for continuous observables with compact support. The essential feature of this natural class of observables is that their support may contain points with infinite free flights. Dealing with such a class of functions is a serious challenge and there is no analogue of it in the finite horizon case. The mixing result for the aforementioned class of functions is obtained via new results: 1) mixing for continuous observables with compact support consisting of configurations at a bounded time from the closest collision; 2) a tightness-type result that allows us to control the configurations with long free flights. To prove 1), we establish a mixing local limit theorem for the Sinai billiard flow with infinite horizon, previously an open question.

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arXiv2024

Stable large deviations for deterministic dynamical systems

We obtain large deviations for a class of dependent random variables in the domain of attraction of an $α$-stable law, $α\in (0, 1)\cup (1, 2]$. This class includes ergodic sums of observables in the domain of attraction of an $α$-stable law driven by Gibbs-Markov maps.

math.PR↗
arXiv2023

Lorentz gas with small scatterers

We prove limit laws for infinite horizon planar periodic Lorentz gases when, as time $n$ tends to infinity, the scatterer size $ρ$ may also tend to zero simultaneously at a sufficiently slow pace. In particular we obtain a non-standard Central Limit Theorem as well as a Local Limit Theorem for the displacement function. To the best of our knowledge, these are the first results on an intermediate case between the two well-studied regimes with superdiffusive $\sqrt{n\log n}$ scaling (i) for fixed infinite horizon configurations -- letting first $n\to \infty$ and then $ρ\to 0$ -- studied e.g.~by Szász \& Varjú (2007) and (ii) Boltzmann-Grad type situations -- letting first $ρ\to 0$ and then $n \to \infty$ -- studied by Marklof \& Tóth (2016).

math.PR↗
arXiv2022

Local large deviations for periodic infinite horizon Lorentz gases

We prove local large deviations for the periodic infinite horizon Lorentz gas viewed as a ${\mathbb Z}^d$-cover ($d=1,2$) of a dispersing billiard. In addition to this specific example, we prove a general result for a class of nonuniformly hyperbolic dynamical systems and observables associated with central limit theorems with nonstandard normalisation.

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arXiv2022

Krickeberg mixing for Z extensions of Gibbs Markov semiflows

We obtain Krickeberg mixing for a class of Z extensions of Gibbs Markov semiflows with roof function and displacement function not in L2, where previous methods have not been employed. This is done via a 'smooth tail' estimate for the isomorphic suspension flow.

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arXiv2021

Strong renewal theorem and local limit theorem in the absence of regular variation

We obtain a strong renewal theorem with infinite mean beyond regular variation, when the underlying distribution belongs to the domain of geometric partial attraction a semistable law with index $α\in (1/2,1]$. In the process we obtain local limit theorems for both finite and infinite mean, that is for the whole range $α\in (0,2)$. We also derive the asymptotics of the renewal function for $α\in (0,1]$.

math.PR↗
arXiv2020

Sharp error term in local limit theorems and mixing for Lorentz gases with infinite horizon

We obtain sharp error rates in the local limit theorem for the Sinai billiard map (one and two dimensional) with infinite horizon. This result allows us to further obtain higher order terms and thus, sharp mixing rates in the speed of mixing of dynamically Hölder observables for the planar and tubular infinite horizon Lorentz gases in the map (discrete time) case. We also obtain an asymptotic estimate for the tail probability of the first return time to the initial cell. In the process, we study families of transfer operators for infinite horizon Sinai billiards perturbed with the free flight function and obtain higher order expansions for the associated families of eigenvalues and eigenprojectors.

math.DS↗
arXiv2020

Limit theorems for wobbly interval intermittent maps

We consider perturbations of interval maps with indifferent fixed points, which we refer to as wobbly interval intermittent maps, for which stable laws for general Hölder observables fail. We obtain limit laws for such maps and Hölder observables. These limit laws are similar to the classical semistable laws previously established for random processes, but certain limitations imposed by the current dynamical set up are reflected in the main result. One of the considered examples is an interval map with a countable number of discontinuities, and to analyse it we need to construct a Markov/Young tower.

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