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Ramachandran Balasubramanian Bruno Calado Hervé Queffélec 《Comptes Rendus Mathematique》2006,342(1):7-10
We extend to the setting of Dirichlet series previous results of Bohr for Taylor series in one variable, themselves generalized by Paulsen, Popescu and Singh or extended to several variables by Aizenberg, Boas and Khavinson. We show in particular that, if , with , then and even slightly better, and , C being an absolute constant. To cite this article: R. Balasubramanian et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
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Xiongping Dai Yu Huang Jun Liu Mingqing Xiao 《Linear algebra and its applications》2012,437(7):1548-1561
We study the finite-step realizability of the joint/generalized spectral radius of a pair of real square matrices and , one of which has rank 1, where . Let denote the spectral radius of a square matrix A. Then we prove that there always exists a finite-length word , for some finite , such thatIn other words, there holds the spectral finiteness property for . Explicit formula for computation of the joint spectral radius is derived. This implies that the stability of the switched system induced by is algorithmically decidable in this case. 相似文献
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Mohammad Daher 《Comptes Rendus Mathematique》2017,355(5):549-552
According to a previous result of the author, if is an interpolation couple, if is weakly LUR, then the complex interpolation spaces have the same property.Here we construct an interpolation couple where is LUR, but where the complex interpolation spaces are not strictly convex. 相似文献
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Guoyou Qian 《Comptes Rendus Mathematique》2017,355(11):1127-1132
Let be a strictly increasing sequence of positive integers ( if ). In 1978, Borwein showed that for any positive integer n, we have , with equality occurring if and only if for . Let be an integer. In this paper, we investigate the sum and show that for any positive integer n, where is a constant depending on r and n. Further, for any integer , we also give a characterization of the sequence such that the equality holds. 相似文献
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Fritz Gesztesy Lance L. Littlejohn Isaac Michael Richard Wellman 《Journal of Differential Equations》2018,264(4):2761-2801
In 1961, Birman proved a sequence of inequalities , for , valid for functions in . In particular, is the classical (integral) Hardy inequality and is the well-known Rellich inequality. In this paper, we give a proof of this sequence of inequalities valid on a certain Hilbert space of functions defined on . Moreover, implies ; as a consequence of this inclusion, we see that the classical Hardy inequality implies each of the inequalities in Birman's sequence. We also show that for any finite , these inequalities hold on the standard Sobolev space . Furthermore, in all cases, the Birman constants in these inequalities are sharp and the only function that gives equality in any of these inequalities is the trivial function in (resp., ). We also show that these Birman constants are related to the norm of a generalized continuous Cesàro averaging operator whose spectral properties we determine in detail. 相似文献
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In this work, we prove the existence of convex solutions to the following k-Hessian equation in the neighborhood of a point , where , is nonnegative near , and . 相似文献
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We present and analyze an iterative method for approximating the Karcher mean of a set of positive definite matrices , , defined as the unique positive definite solution of the matrix equation . 相似文献
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Neel Patel 《Journal of Differential Equations》2018,264(3):1841-1885
We consider continuation criteria for the three-dimensional relativistic Vlasov–Maxwell system. When the particle density, , is compactly supported at , we prove , where and is arbitrarily small, is a continuation criteria. Our continuation criteria is an improvement in the range to the previously best known criteria due to Kunze [7]. We also consider continuation criteria when has noncompact support. In this regime, Luk–Strain [9] proved that is a continuation criteria for . We improve this result to . Finally, we build on another result by Luk–Strain [8]. The authors proved boundedness of momentum support on a fixed two-dimensional plane is a sufficient continuation criteria. We prove the same result even if the plane varies continuously in time. 相似文献