Quasinormal families of meromorphic functions.
Xuecheng Pang, Shahar Nevo, Lawrence Zalcman (2005)
Revista Matemática Iberoamericana
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Xuecheng Pang, Shahar Nevo, Lawrence Zalcman (2005)
Revista Matemática Iberoamericana
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Camil Muscalu, Jill Pipher, Terence Tao, Christoph Thiele (2006)
Revista Matemática Iberoamericana
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We prove that classical Coifman-Meyer theorem holds on any polidisc T or arbitrary dimension d ≥ 1.
Zoltán Buczolich (2005)
Revista Matemática Iberoamericana
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In this paper we give a complete answer to the famous gradient problem of C. E. Weil. On an open set G ⊂ R we construct a differentiable function f: G → R for which there exists an open set Ω ⊂ R such that ∇f(p) ∈ Ω for a p ∈ G but ∇f(q) ∉ Ω for almost every q ∈ G. This shows that the Denjoy-Clarkson property does not hold in higher dimensions.
Karlheinz Gröchenig (2006)
Revista Matemática Iberoamericana
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We investigate the properties an exotic symbol class of pseudodifferential operators, Sjöstrand's class, with methods of time-frequency analysis (phase space analysis). Compared to the classical treatment, the time-frequency approach leads to striklingly simple proofs of Sjöstrand's fundamental results and to far-reaching generalizations.
Charles Fefferman (2005)
Revista Matemática Iberoamericana
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Suppose that, for each point x in a given subset E ⊂ R, we are given an m-jet f(x) and a convex, symmetric set σ(x) of m-jets at x. We ask whether there exist a function F ∈ C(R) and a finite constant M, such that the m-jet of F at x belongs to f(x) + Mσ(x) for all x ∈ E. We give a necessary and sufficient condition for the existence of such F, M, provided each σ(x) satisfies a condition that we call "Whitnet w-convexity".
M. Fabian, P. Hájek, V. Montesinos, V. Zizler (2005)
Revista Matemática Iberoamericana
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A quantitative version of Krein's Theorem on convex hulls of weak compact sets is proved. Some applications to weakly compactly generated Banach spaces are given.
Yahya Ould Hamidoune, Alain Plagne (2005)
Revista Matemática Iberoamericana
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Gérard Bourdaud, Massimo Lanza de Cristoforis, Winfried Sickel (2006)
Revista Matemática Iberoamericana
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We characterize the set of all functions f of R to itself such that the associated superposition operator T: g → f º g maps the class BV (R) into itself. Here BV (R), 1 ≤ p < ∞, denotes the set of primitives of functions of bounded p-variation, endowed with a suitable norm. It turns out that such an operator is always bounded and sublinear. Also, consequences for the boundedness of superposition operators defined on Besov spaces B ...
Herbert Koch, Winfried Sickel (2002)
Revista Matemática Iberoamericana
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Themis Mitsis (2004)
Revista Matemática Iberoamericana
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We prove that a set containing translates of every 2-plane must have full Hausdorff dimension.
P. Batchourine, C. Fefferman (2007)
Revista Matemática Iberoamericana
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Anthony Carbery, Fulvio Ricci, James Wright (2003)
Revista Matemática Iberoamericana
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Martin T. Barlow (2004)
Revista Matemática Iberoamericana
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David Drasin, Swati Sastry (2003)
Revista Matemática Iberoamericana
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The authors construct a periodic quasiregular function of any finite order p, 1 < p < infinity. This completes earlier work of O. Martio and U. Srebro.
Lidia Maniccia, Marco Mughetti (2006)
Revista Matemática Iberoamericana
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We prove Fefferman's SAK Principle for a class of hypoelliptic operators on R whose nonnegative symbol vanishes anisotropically on the characteristic manifold.