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Failure of analytic hypoellipticity in a class of differential operators

Ovidiu Costin, Rodica D. Costin (2003)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

For the hypoelliptic differential operators P = x 2 + x k y - x l t 2 introduced by T. Hoshiro, generalizing a class of M. Christ, in the cases of k and l left open in the analysis, the operators P also fail to be analytic hypoelliptic (except for ( k , l ) = ( 0 , 1 ) ), in accordance with Treves’ conjecture. The proof is constructive, suitable for generalization, and relies on evaluating a family of eigenvalues of a non-self-adjoint operator.

Faisceaux maximaux de fonctions associées à un opérateur elliptique du second ordre

Denis Feyel, A. de La Pradelle (1976)

Annales de l'institut Fourier

Soit F le faisceau des sursolutions variationnelles d’un opérateur différentiel elliptique du second ordre à coefficients L loc . Soit F ^ le faisceau des régularitées essentielles inférieures des éléments de F . On démontre que F ^ est contenu dans un seul préfaisceau F * maximal de cônes convexes de fonctions s.c.i. > - vérifiant le principe du minimum sur une base d’ouverts suffisamment petits. On démontre que F * possède toutes les bonnes propriétés d’une théorie locale du potentiel.

Familles de convexes invariantes et équations de diffusion-réaction

Christine Reder (1982)

Annales de l'institut Fourier

Pour localiser la solution d’un système de diffusion-réaction, il suffit de construire une famille de convexes ( K t ) t 0 , invariante par rapport au champ de vecteurs associé à ce système; la solution est alors incluse dans K t à l’instant t dès qu’elle est contenue dans K 0 à l’instant zéro. Les fonctions d’appui associées à de telles familles de convexes sont solutions d’un système différentiel, mais celui-ci peut également engendrer des familles non invariantes.

Feedback stabilization of Navier–Stokes equations

Viorel Barbu (2003)

ESAIM: Control, Optimisation and Calculus of Variations

One proves that the steady-state solutions to Navier–Stokes equations with internal controllers are locally exponentially stabilizable by linear feedback controllers provided by a L Q control problem associated with the linearized equation.

Feedback stabilization of Navier–Stokes equations

Viorel Barbu (2010)

ESAIM: Control, Optimisation and Calculus of Variations

One proves that the steady-state solutions to Navier–Stokes equations with internal controllers are locally exponentially stabilizable by linear feedback controllers provided by a LQ control problem associated with the linearized equation.

Fine topology and quasilinear elliptic equations

Juha Heinonen, Terro Kilpeläinen, Olli Martio (1989)

Annales de l'institut Fourier

It is shown that the ( 1 , p ) -fine topology defined via a Wiener criterion is the coarsest topology making all supersolutions to the p -Laplace equation div ( | u | p - 2 u ) = 0 continuous. Fine limits of quasiregular and BLD mappings are also studied.

Finite-dimensional Pullback Attractors for Non-autonomous Newton-Boussinesq Equations in Some Two-dimensional Unbounded Domains

Cung The Anh, Dang Thanh Son (2014)

Bulletin of the Polish Academy of Sciences. Mathematics

We study the existence and long-time behavior of weak solutions to Newton-Boussinesq equations in two-dimensional domains satisfying the Poincaré inequality. We prove the existence of a unique minimal finite-dimensional pullback D σ -attractor for the process associated to the problem with respect to a large class of non-autonomous forcing terms.

Finite-dimensional pullback attractors for parabolic equations with Hardy type potentials

Cung The Anh, Ta Thi Hong Yen (2011)

Annales Polonici Mathematici

Using the asymptotic a priori estimate method, we prove the existence of a pullback -attractor for a reaction-diffusion equation with an inverse-square potential in a bounded domain of N (N ≥ 3), with the nonlinearity of polynomial type and a suitable exponential growth of the external force. Then under some additional conditions, we show that the pullback -attractor has a finite fractal dimension and is upper semicontinuous with respect to the parameter in the potential.

Finite-dimensionality of 2-D micropolar fluid flow with periodic boundary conditions

Piotr Szopa (2007)

Applicationes Mathematicae

This paper is devoted to proving the finite-dimensionality of a two-dimensional micropolar fluid flow with periodic boundary conditions. We define the notions of determining modes and nodes and estimate their number. We check how the distribution of the forces and moments through modes influences the estimate of the number of determining modes. We also estimate the dimension of the global attractor. Finally, we compare our results with analogous results for the Navier-Stokes equation.

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