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On the finite blocking property

Thierry Monteil (2005)

Annales de l’institut Fourier

A planar polygonal billiard 𝒫 is said to have the finite blocking property if for every pair ( O , A ) of points in 𝒫 there exists a finite number of “blocking” points B 1 , , B n such that every billiard trajectory from O to A meets one of the B i ’s. Generalizing our construction of a counter-example to a theorem of Hiemer and Snurnikov, we show that the only regular polygons that have the finite blocking property are the square, the equilateral triangle and the hexagon. Then we extend this result to translation surfaces....

On the formal first cocycle equation for iteration groups of type II

Harald Fripertinger, Ludwig Reich (2012)

ESAIM: Proceedings

Let x be an indeterminate over ℂ. We investigate solutions α ( s , x ) = n 0 α n ( s ) x n , αn : ℂ → ℂ, n ≥ 0, of the first cocycle equation α ( s + t , x ) = α ( s , x ) α t , F ( s , x ) , s , t , ( Co 1 ) in ℂ [[x]], the ring of formal power series over ℂ, where (F(s,x))s ∈ ℂ is an iteration group of type II, i.e. it is a solution of the translation equation F ( s + t , x ) = F ( s , F ( t , x ) ) , s , t , ( T ) of the form F(s,x) ≡ x + ck(s)xk mod xk+1, where k ≥ 2 and ck ≠ 0 is necessarily an additive function. It is easy to prove that the coefficient functions αn(s) of α ( s , x ) = 1 + n 1 α n ( s ) x n are polynomials in ck(s).It is possible to replace...

On the g -entropy and its Hudetz correction

Beloslav Riečan (2002)

Kybernetika

The Hudetz correction of the fuzzy entropy is applied to the g -entropy. The new invariant is expressed by the Hudetz correction of fuzzy entropy.

On the GBDT Version of the Bäcklund-Darboux Transformation and its Applications to Linear and Nonlinear Equations and Weyl Theory

A. Sakhnovich (2010)

Mathematical Modelling of Natural Phenomena

A general theorem on the GBDT version of the Bäcklund-Darboux transformation for systems depending rationally on the spectral parameter is treated and its applications to nonlinear equations are given. Explicit solutions of direct and inverse problems for Dirac-type systems, including systems with singularities, and for the system auxiliary to the N-wave equation are reviewed. New results on explicit construction of the wave functions for radial...

On the genesis of symbolic dynamics as we know it

Ethan M. Coven, Zbigniew H. Nitecki (2008)

Colloquium Mathematicae

We trace the beginning of symbolic dynamics-the study of the shift dynamical system-as it arose from the use of coding to study recurrence and transitivity of geodesics. It is our assertion that neither Hadamard's 1898 paper, nor the Morse-Hedlund papers of 1938 and 1940, which are normally cited as the first instances of symbolic dynamics, truly present the abstract point of view associated with the subject today. Based in part on the evidence of a 1941 letter from Hedlund to Morse, we place the...

On the global maximum of the solution to a stochastic heat equation with compact-support initial data

Mohammud Foondun, Davar Khoshnevisan (2010)

Annales de l'I.H.P. Probabilités et statistiques

Consider a stochastic heat equation ∂tu=κ  ∂xx2u+σ(u)ẇ for a space–time white noise ẇ and a constant κ>0. Under some suitable conditions on the initial function u0 and σ, we show that the quantities lim sup t→∞t−1sup x∈Rln El(|ut(x)|2) and lim sup t→∞t−1ln E(sup x∈R|ut(x)|2) are equal, as well as bounded away from zero and infinity by explicit multiples of 1/κ. Our proof works by demonstrating quantitatively that the peaks of the stochastic process x↦ut(x) are highly concentrated...

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