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Range of density measures

Martin Sleziak, Miloš Ziman (2009)

Acta Mathematica Universitatis Ostraviensis

We investigate some properties of density measures – finitely additive measures on the set of natural numbers extending asymptotic density. We introduce a class of density measures, which is defined using cluster points of the sequence A ( n ) n as well as cluster points of some other similar sequences. We obtain range of possible values of density measures for any subset of . Our description of this range simplifies the description of Bhashkara Rao and Bhashkara Rao [Bhaskara Rao, K. P. S., Bhaskara Rao,...

Rank and spectral multiplicity

Sébastien Ferenczi, Jan Kwiatkowski (1992)

Studia Mathematica

For a dynamical system (X,T,μ), we investigate the connections between a metric invariant, the rank r(T), and a spectral invariant, the maximal multiplicity m(T). We build examples of systems for which the pair (m(T),r(T)) takes values (m,m) for any integer m ≥ 1 or (p-1, p) for any prime number p ≥ 3.

Recent progress on the Kakeya conjecture.

Nets Katz, Terence Tao (2002)

Publicacions Matemàtiques

We survey recent developments on the Kakeya problem.[Proceedings of the 6th International Conference on Harmonic Analysis and Partial Differential Equations, El Escorial (Madrid), 2002].

Recouvrements, derivation des mesures et dimensions.

Patrice Assouad, Thierry Quentin de Gromard (2006)

Revista Matemática Iberoamericana

Let X be a set with a symmetric kernel d (not necessarily a distance). The space (X,d) is said to have the weak (resp. strong) covering property of degree ≤ m [briefly prf(m) (resp. prF(m))], if, for each family B of closed balls of (X,d) with radii in a decreasing sequence (resp. with bounded radii), there is a subfamily, covering the center of each element of B, and of order ≤ m (resp. splitting into m disjoint families). Since Besicovitch, covering properties are known to be the main tool for...

Rectifiability and parameterization of intrinsic regular surfaces in the Heisenberg group

Bernd Kirchheim, Francesco Serra Cassano (2004)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

We construct an intrinsic regular surface in the first Heisenberg group 1 3 equipped wiht its Carnot-Carathéodory metric which has euclidean Hausdorff dimension  2 . 5 . Moreover we prove that each intrinsic regular surface in this setting is a 2 -dimensional topological manifold admitting a 1 2 -Hölder continuous parameterization.

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