Displaying similar documents to “Codimension one symplectic foliations.”

Multi-parameter paraproducts.

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.

Time-frequency analysis of Sjöstrand's class.

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.

SAK principle for a class of Grushin-type operators.

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.

Solution to the gradient problem of C.E. Weil.

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.