共查询到20条相似文献,搜索用时 31 毫秒
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In this paper we study the limit cycles of the Liénard differential system of the form , or its equivalent system , . We provide sufficient conditions in order that the system exhibits at least n or exactly n limit cycles. 相似文献
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Yong-Gao Chen 《Journal of Number Theory》2003,100(2):326-331
Let p1,p2,… be the sequence of all primes in ascending order. The following result is proved: for any given positive integer k and any given , there exist infinitely many positive integers n with
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We estimate the norm of the almost Mathieu operator , regarded as an element in the rotation C*-algebra . In the process, we prove for every λ∈R and the inequality
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In this paper we consider two von Neumann subalgebras and of a type II1 factor . For a map φ on , we define
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Satit Saejung 《数学物理学报(B辑英文版)》2011,31(3):1035-1040
We present a short and simple proof of the recent result of Yang and Wang [12]. Stimulated by their idea, two geometric parameters U~ax(ε) and βx (ε), both related to Gao’s modulus of U-convexity of a Banach space X, are introduced. Their properties and the relationships with normal structure are studied. Some existing results involving normal structure and fixed points for non-expansive mappings in Banach spaces are improved. 相似文献
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Let . We prove that a subset of , where p is a prime number, with cardinality larger than such that its subset sums do not cover has an automorphic image which is rather concentrated; more precisely, there exists s prime to p such that
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Liang-Xue Peng 《Topology and its Applications》2010,157(2):378-876
In this note, we comment on D-spaces, linearly D-spaces and transitively D-spaces. We show that every meta-Lindelöf space is transitively D. If X is a weak -refinable TD-scattered space, then X is transitively D, where TD is the class of all transitively D-spaces. If X is a weak -refinable -scattered space, then X is a D-space, where is the class of all D-spaces, and hence every weak -refinable (or submetacompact) scattered space is a D-space. This gives a positive answer to a question mentioned by Martínez and Soukup. In the last part of this note, we show that if X is a weak -refinable space then X is linearly D. 相似文献
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Hans-Otto Walther 《Journal of Differential Equations》2003,195(1):46-65
Let h>0, open, and continuously differentiable. If f satisfies two mild additional smoothness conditions then the set
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Let Ω be a smooth bounded domain in , with N?5, a>0, α?0 and . We show that the exponent plays a critical role regarding the existence of least energy (or ground state) solutions of the Neumann problem
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Let be a self-adjoint extension in of a fixed symmetric operator A in . An analytic characterization of the eigenvalues of is given in terms of the Q-function and the parameter function in the Krein-Naimark formula. Here K and are Krein spaces and it is assumed that locally has the same spectral properties as a self-adjoint operator in a Pontryagin space. The general results are applied to a class of boundary value problems with λ-dependent boundary conditions. 相似文献
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Michael Paluch 《Journal of Pure and Applied Algebra》2008,212(12):2583-2593
Let be a small category. For an -diagram X and -diagrams A and B of pointed spaces, each pairing X∧A→B satisfying the projection formula induces a pairing . In this note we show that there is an induced pairing of homotopy spectral sequences compatible with abutments in the sense that
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Yossi Lonke 《Advances in Mathematics》2003,176(2):175-186
The Lp-cosine transform of an even, continuous function is defined by