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Area and Hausdorff Dimension of Julia Sets of Entire Functions
 Trans. Amer. Math. Soc
, 1987
"... Introduction There is no known rational function R whose Julia set J has positive area and yet is not the whole Riemann sphere. (Indeed there is as yet no example for which J is proved to be a proper subset of the sphere with Hausdorff dimension two.) On the other hand, when the forward orbits of th ..."
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Cited by 48 (1 self)
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Introduction There is no known rational function R whose Julia set J has positive area and yet is not the whole Riemann sphere. (Indeed there is as yet no example for which J is proved to be a proper subset of the sphere with Hausdorff dimension two.) On the other hand, when the forward orbits of the critical points do not accumulate on J, the map R is expanding and Sullivan shows dim(J) < 2 (in fact J has positive finite measure in its dimension [S]). So disregarding the case J = C , it is fairly hard to find large Julia sets. The purpose of this note is to describe a contrasting situation for some entire functions. We consider two families of functions: {f(z) = le z : l 0} (the "exponential family") {f(z) = sin(az+b) : a 0} (the "sine family") Each of these families is "t
Nonsingular transformations and spectral analysis of measures
 Bull. Soc. Math. France
, 1991
"... RÉSUMÉ. — Ce travail approfondit les interactions qui existent entre l’analyse harmonique des mesures et l’étude spectrale des systèmes dynamiques non singuliers. Il est centre ́ sur l’étude de sousgroupes remarquables du cercle, groupes de valeurs propres, groupes de quasiinvariance des mesu ..."
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Cited by 13 (0 self)
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RÉSUMÉ. — Ce travail approfondit les interactions qui existent entre l’analyse harmonique des mesures et l’étude spectrale des systèmes dynamiques non singuliers. Il est centre ́ sur l’étude de sousgroupes remarquables du cercle, groupes de valeurs propres, groupes de quasiinvariance des mesures..., dont les exemples les plus naturels sont définis par des conditions diophantiennes. La conjonction des points de vue permet d’obtenir nombre de résultats nouveaux dans les deux théories, y compris dans des problèmes classique d’analyse de Fourier. ABSTRACT. — This work explores in depth the interactions existing between harmonic analysis of measures and spectral theory of nonsingular dynamical systems. It focuses on the study of some classes of remarkable subgroups of the circle: eigenvalue groups, groups of quasiinvariance of measures..., the most natural examples of which are defined by diophantine conditions. The conjonction of these points of view leads to many new results in both theories, including some classical problems in Fourier analysis. 1.
Fractals in Noncommutative Geometry
 in the Proceedings of the Conference ”Mathematical Physics in Mathematics and Physics”, Siena 2000, Edited by R. Longo, Fields Institute Communications
, 2001
"... Abstract. To any spectral triple (A, D, H) a dimension d is associated, in analogy with the Hausdorff dimension for metric spaces. Indeed d is the unique number, if any, such that D  −d has non trivial logarithmic Dixmier trace. Moreover, when d ∈ (0, ∞), there always exists a singular trace which ..."
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Cited by 9 (6 self)
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Abstract. To any spectral triple (A, D, H) a dimension d is associated, in analogy with the Hausdorff dimension for metric spaces. Indeed d is the unique number, if any, such that D  −d has non trivial logarithmic Dixmier trace. Moreover, when d ∈ (0, ∞), there always exists a singular trace which is finite nonzero on D  −d, giving rise to a noncommutative integration on A. Such results are applied to fractals in R, using Connes ’ spectral triple, and to limit fractals in R n, a class which generalises selfsimilar fractals, using a new spectral triple. The noncommutative dimension or measure can be computed in some cases. They are shown to coincide with the (classical) Hausdorff dimension and measure in the case of selfsimilar fractals. 1 Introduction. This paper is both a survey and an announcement of results concerning singular traces on B(H), and their application to the study of fractals in the framework of
Actions of F∞ whose II1 factors and orbit equivalence relations have prescribed fundamental group
, 2008
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Prospects for mathematical logic in the twentyfirst century
 BULLETIN OF SYMBOLIC LOGIC
, 2002
"... The four authors present their speculations about the future developments of mathematical logic in the twentyfirst century. The areas of recursion theory, proof theory and logic for computer science, model theory, and set theory are discussed independently. ..."
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Cited by 8 (0 self)
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The four authors present their speculations about the future developments of mathematical logic in the twentyfirst century. The areas of recursion theory, proof theory and logic for computer science, model theory, and set theory are discussed independently.
On Hausdorff’s moment problem in higher dimensions. Published on web at http://abel.math.harvard.edu/∼knill/preprints/stability.ps
, 1997
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Subdiffusive quantum transport for 3DHamiltonians with absolutely continuous spectra
"... Both in the 3D Anderson model at low disorder and in 3D quasicrystals, the local density of states is expected to be absolutely continuous, although the quantum transport is diusive or subdiusive respectively. By studying sums of 1D models with wellunderstood spectral and transport properties, we e ..."
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Cited by 2 (1 self)
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Both in the 3D Anderson model at low disorder and in 3D quasicrystals, the local density of states is expected to be absolutely continuous, although the quantum transport is diusive or subdiusive respectively. By studying sums of 1D models with wellunderstood spectral and transport properties, we exhibit a 3D model with absolutely continuous spectrum for which the diusion exponent characterizing the growth of the mean square displacement is only slightly bigger than imposed by Guarneri's lower bound. Keywords: anomalous quantum transport, fractal measures Quantum diusion in aperiodic media is slowed down due to destructive interference phenomena. The most prominent example is the Anderson model describing an electron in a disordered potential. In low dimension or for a strong disordered potential, the motion is completely localized and the spectrum is known to be purepoint (see [1] and references therein). On the other hand, scaling arguments and numerical calculations [14] show ...
Absolute continuity for some onedimensional processes
, 2008
"... We introduce an elementary method for proving the absolute continuity of the time marginals of onedimensional processes. It is based on a comparison between the Fourier transform of such time marginals with those of the onestep Euler approximation of the underlying process. We obtain some absolute ..."
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We introduce an elementary method for proving the absolute continuity of the time marginals of onedimensional processes. It is based on a comparison between the Fourier transform of such time marginals with those of the onestep Euler approximation of the underlying process. We obtain some absolute continuity results for stochastic differential equations with Hölder continuous coefficients. Furthermore, we allow such coefficients to be random and to depend on the whole path of the solution. We also show how it can be extended to some stochastic partial differential equations, and to some Lévydriven stochastic differential equations. In the cases under study, the Malliavin calculus cannot be used, because the solution in generally not Malliavindifferentiable.
The Sidon constant of sets with three elements. arxiv.org/ math/0102145
, 2001
"... We solve an elementary minimax problem and obtain the exact value of the Sidon constant for sets with three elements {n0, n1, n2}: it is sec(π/2n) for n = max ni − nj/gcd(n1 − n0, n2 − n0). 1 ..."
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We solve an elementary minimax problem and obtain the exact value of the Sidon constant for sets with three elements {n0, n1, n2}: it is sec(π/2n) for n = max ni − nj/gcd(n1 − n0, n2 − n0). 1