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We study the Keller–Segel system in when the chemoattractant concentration is described by a parabolic equation. We prove that the critical space, with some similarity to the elliptic case, is that the initial bacteria density satisfies , , and that the chemoattractant concentration satisfies . In these spaces, we prove that small initial data give rise to global solutions that vanish as the heat equation for large times and that exhibit a regularizing effect of hypercontractivity type. To cite this article: L. Corrias, B. Perthame, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
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We derive necessary and sufficient conditions for a one-dimensional periodic Schrödinger (i.e., Hill) operator in to be a spectral operator of scalar type. The conditions demonstrate the remarkable fact that the property of a Hill operator being a spectral operator is independent of smoothness (or even analyticity) properties of the potential V. To cite this article: F. Gesztesy, V. Tkachenko, C. R. Acad. Sci. Paris, Ser. I 343 (2006). 相似文献
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Let be a Lipschitz domain and Γ be a relatively open and non-empty subset of its boundary ?Ω. We show that the solution to the linear first-order system:(1) vanishes if and . In particular, square-integrable solutions ζ of (1) with vanish. As a consequence, we prove that: is a norm if with , for some with as well as . We also give a new and different proof for the so-called ‘infinitesimal rigid displacement lemma’ in curvilinear coordinates: Let , , satisfy for some with . Then there exists a constant translation vector and a constant skew-symmetric matrix , such that . 相似文献
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《Journal de Mathématiques Pures et Appliquées》2006,85(1):2-16
Let ω be a domain in and let be a smooth immersion. The main purpose of this paper is to establish a “nonlinear Korn inequality on the surface ”, asserting that, under ad hoc assumptions, the -distance between the surface and a deformed surface is “controlled” by the -distance between their fundamental forms. Naturally, the -distance between the two surfaces is only measured up to proper isometries of .This inequality implies in particular the following interesting per se sequential continuity property for a sequence of surfaces. Let , , be mappings with the following properties: They belong to the space ; the vector fields normal to the surfaces , , are well defined a.e. in ω and they also belong to the space ; the principal radii of curvature of the surfaces , , stay uniformly away from zero; and finally, the fundamental forms of the surfaces converge in toward the fundamental forms of the surface as . Then, up to proper isometries of , the surfaces converge in toward the surface as .Such results have potential applications to nonlinear shell theory, the surface being then the middle surface of the reference configuration of a nonlinearly elastic shell. 相似文献
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We obtain two-weighted norm inequalities for oscillatory integral operators of convolution type on the line whose phases are of finite type. The conditions imposed on the weights involve geometrically-defined maximal functions, and the inequalities are best-possible in the sense that they imply the full mapping properties of the oscillatory integrals. Our results build on work of Carbery, Soria, Vargas and the first author. 相似文献
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In this paper, we study the existence, uniqueness and the probabilistic representation of the weak solutions of quasi-linear parabolic and elliptic partial differential equations (PDEs) in the Sobolev space . For this, we study first the solutions of forward–backward stochastic differential equations (FBSDEs) with smooth coefficients, regularity of solutions and their connection with classical solutions of quasi-linear parabolic PDEs. Then using the approximation procedure, we establish their convergence in the Sobolev space to the solutions of the FBSDES in the space . This gives a connection with the weak solutions of quasi-linear parabolic PDEs. Finally, we study the unique weak solutions of quasi-linear elliptic PDEs using the solutions of the FBSDEs on infinite horizon. 相似文献
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Douglas P. Hardin Michael C. Northington Alexander M. Powell 《Applied and Computational Harmonic Analysis》2018,44(2):294-311
A sharp version of the Balian–Low theorem is proven for the generators of finitely generated shift-invariant spaces. If generators are translated along a lattice to form a frame or Riesz basis for a shift-invariant space V, and if V has extra invariance by a suitable finer lattice, then one of the generators must satisfy , namely, . Similar results are proven for frames of translates that are not Riesz bases without the assumption of extra lattice invariance. The best previously existing results in the literature give a notably weaker conclusion using the Sobolev space ; our results provide an absolutely sharp improvement with . Our results are sharp in the sense that cannot be replaced by for any . 相似文献
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Masoud Hassani 《Comptes Rendus Mathematique》2017,355(11):1133-1137
In this paper, we study the irreducible representation of in . This action preserves a quadratic form with signature . Thus, it acts conformally on the 3-dimensional Einstein universe . We describe the orbits induced in and its complement in . This work completes the study in [2], and is one element of the classification of cohomogeneity one actions on [5]. 相似文献
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Xiaopeng Zhao 《Comptes Rendus Mathematique》2017,355(3):310-317
This paper discusses the large-time behavior of solutions for a new Hall–MHD system in . Using the Fourier splitting method, we establish the upper bound of the time-decay rate in for weak solutions. 相似文献
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Paolo Boggiatto Carmen Fernández Antonio Galbis 《Applied and Computational Harmonic Analysis》2017,42(1):65-87
Inspired by results of Kim and Ron, given a Gabor frame in , we determine a non-countable generalized frame for the non-separable space of the Besicovic almost periodic functions. Gabor type frames for suitable separable subspaces of are constructed. We show furthermore that Bessel-type estimates hold for the AP norm with respect to a countable Gabor system using suitable almost periodic norms of sequences. 相似文献
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Philippe G. Ciarlet Liliana Gratie Cristinel Mardare 《Comptes Rendus Mathematique》2005,341(3):201-206
The main purpose of this Note is to show how a ‘nonlinear Korn's inequality on a surface’ can be established. This inequality implies in particular the following interesting per se sequential continuity property for a sequence of surfaces. Let ω be a domain in , let be a smooth immersion, and let , , be mappings with the following properties: They belong to the space ; the vector fields normal to the surfaces , , are well defined a.e. in ω and they also belong to the space ; the principal radii of curvature of the surfaces stay uniformly away from zero; and finally, the three fundamental forms of the surfaces converge in toward the three fundamental forms of the surface as . Then, up to proper isometries of , the surfaces converge in toward the surface as . To cite this article: P.G. Ciarlet et al., C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
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Michael Cuntz 《Journal of Algebra》2008,319(11):4536-4558
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We present a new optimal construction of a semi-separated pair decomposition (i.e., SSPD) for a set of n points in . In the new construction each point participates in a few pairs, and it extends easily to spaces with low doubling dimension. This is the first optimal construction with these properties.As an application of the new construction, for a fixed , we present a new construction of a t-spanner with edges and maximum degree that has a separator of size . 相似文献