1,494 research outputs found
Cauchy distributions for the integrable standard map
We consider the integrable (zero perturbation) two--dimensional standard map,
in light of current developments on ergodic sums of irrational rotations, and
recent numerical evidence that it might possess non-trivial q-Gaussian
statistics. Using both classical and recent results, we show that the phase
average of the sum of centered positions of an orbit, for long times and after
normalization, obeys the Cauchy distribution (a q-Gaussian with q=2), while for
almost all individual orbits such a sum does not obey any distribution at all.
We discuss the question of existence of distributions for KAM tori.Comment: 6 pages, 2 figure
A temporal Central Limit Theorem for real-valued cocycles over rotations
We consider deterministic random walks on the real line driven by irrational
rotations, or equivalently, skew product extensions of a rotation by
where the skewing cocycle is a piecewise constant mean zero function with a
jump by one at a point . When is badly approximable and
is badly approximable with respect to , we prove a Temporal Central
Limit theorem (in the terminology recently introduced by D.Dolgopyat and
O.Sarig), namely we show that for any fixed initial point, the occupancy random
variables, suitably rescaled, converge to a Gaussian random variable. This
result generalizes and extends a theorem by J. Beck for the special case when
is quadratic irrational, is rational and the initial point is
the origin, recently reproved and then generalized to cover any initial point
using geometric renormalization arguments by Avila-Dolgopyat-Duryev-Sarig
(Israel J., 2015) and Dolgopyat-Sarig (J. Stat. Physics, 2016). We also use
renormalization, but in order to treat irrational values of , instead of
geometric arguments, we use the renormalization associated to the continued
fraction algorithm and dynamical Ostrowski expansions. This yields a suitable
symbolic coding framework which allows us to reduce the main result to a CLT
for non homogeneous Markov chains.Comment: a few typos corrected, 28 pages, 4 figure
No temporal distributional limit theorem for a.e. irrational translation
Bromberg and Ulcigrai constructed piecewise smooth functions f on the torus
such that the set of angles alpha for which the Birkhoff sums of f with respect
to the irrational translation by alpha satisfies a temporal distributional
limit theorem along the orbit of a.e. x has Hausdorff dimension one. We show
that the Lebesgue measure of this set of angles is equal to zero
A Computable Economist’s Perspective on Computational Complexity
A computable economist's view of the world of computational complexity theory is described. This means the model of computation underpinning theories of computational complexity plays a central role. The emergence of computational complexity theories from diverse traditions is emphasised. The unifications that emerged in the modern era was codified by means of the notions of efficiency of computations, non-deterministic computations, completeness, reducibility and verifiability - all three of the latter concepts had their origins on what may be called 'Post's Program of Research for Higher Recursion Theory'. Approximations, computations and constructions are also emphasised. The recent real model of computation as a basis for studying computational complexity in the domain of the reals is also presented and discussed, albeit critically. A brief sceptical section on algorithmic complexity theory is included in an appendix
A Computable Economist’s Perspective on Computational Complexity
A computable economist.s view of the world of computational complexity theory is described. This means the model of computation underpinning theories of computational complexity plays a central role. The emergence of computational complexity theories from diverse traditions is emphasised. The unifications that emerged in the modern era was codified by means of the notions of efficiency of computations, non-deterministic computations, completeness, reducibility and verifiability - all three of the latter concepts had their origins on what may be called "Post's Program of Research for Higher Recursion Theory". Approximations, computations and constructions are also emphasised. The recent real model of computation as a basis for studying computational complexity in the domain of the reals is also presented and discussed, albeit critically. A brief sceptical section on algorithmic complexity theory is included in an appendix.
On the metric upper density of Birkhoff sums for irrational rotations
This article examines the value distribution of for almost every where is
ranging over a long interval and is a -periodic function with
discontinuities or logarithmic singularities at rational numbers. We show that
for in a set of positive upper density, the order of is
of Khintchine-type, unless the logarithmic singularity is symmetric.
Additionally, we show the asymptotic sharpness of the Denjoy-Koksma inequality
for such , with applications in the theory of numerical integration. Our
method also leads to a generalized form of the classical Borel-Bernstein
Theorem that allows very general modularity conditions.Comment: 34 pages, comments are welcom
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