排序方式: 共有17条查询结果,搜索用时 58 毫秒
1.
2.
丘京辉 《数学物理学报(B辑英文版)》1998,(3)
0IntroductionIntile1930's,thefirstoped1flappingtheoremforFr6clletspaceswasprovedbyS.B....htll].Sincethedtilevariousextellsiollsoftheopenmappingtheoremhaveapl)earedillsuccessiollforitsapplications(fordetails,see[4]).In1958,V.PtAkfoundoutthatoped1llappillgtheoremsareconllectedwithsolllecompleteness,alldheobtainedastrikillgextensiollofBallach'sclassicaltlleoreul,whichpoilltsoutthatcontinuouslillearmapsfi.olllB-colllpletespacesolltobarrelledspacesareoped['].1111965,T.Husaingaveaninlportalltope… 相似文献
3.
4.
Deguang Han 《Transactions of the American Mathematical Society》2008,360(6):3307-3326
Let be a frame for a Hilbert space . We investigate the conditions under which there exists a dual frame for which is also a Parseval (or tight) frame. We show that the existence of a Parseval dual is equivalent to the problem whether can be dilated to an orthonormal basis (under an oblique projection). A necessary and sufficient condition for the existence of Parseval duals is obtained in terms of the frame excess. For a frame induced by a projective unitary representation of a group , it is possible that can have a Parseval dual, but does not have a Parseval dual of the same type. The primary aim of this paper is to present a complete characterization for all the projective unitary representations such that every frame (with a necessary lower frame bound condition) has a Parseval dual of the same type. As an application of this characterization together with a result about lattice tiling, we prove that every Gabor frame (again with the same necessary lower frame bound condition) has a Parseval dual of the same type if and only if the volume of the fundamental domain of is less than or equal to .
5.
Deguang Han 《Journal of Functional Analysis》2009,256(1):129-1472
Let K and L be two full-rank lattices in Rd. We give a complete characterization for all the Gabor frames that admit tight dual of the same type. The characterization is given in terms of the center-valued trace of the von Neumann algebra generated by the left regular projective unitary representations associated with the time-frequency lattice K×L. Two applications of this characterization were obtained: (i) We are able to prove that every Gabor frame has a tight dual if and only if the volume of K×L is less than or equal to . (ii) We are able to obtain sufficient or necessary conditions for the existence of tight Gabor pseudo-duals for subspace Gabor frames in various cases. In particular, we prove that every subspace Gabor frame has a tight Gabor pseudo-dual if either the volume or v(K×L)?2. Moreover, if K=αZd, L=βZd with αβ=1, then a subspace Gabor frame G(g,L,K) has a tight Gabor pseudo-dual only when G(g,L,K) itself is already tight. 相似文献
6.
Based on new bounds on the values of Krawtchoukpolynomials, we improve earlier known estimates forcomponents of the distance distributions of BCH codes and theirduals. Moreover, we show that if one uses estimates on Krawtchoukpolynomials for bounding the error term in the binomial approximationto the distance distribution of BCH codes, the given results are actuallythe best possible. One of the advantages of the proposed approach isthat it provides estimates with no restrictions on the minimumdistance of the code. 相似文献
7.
Recently, Gulati and Craven and Mond and Egudo established strict converse duality theorems for some of Mond-Weir duals for nonlinear programming problems. Here, we establish various duality theorems under weaker convexity conditions that are different from those of Gulati and Craven, Mond and Weir, and Mond and Egudo.The first author is thankful to the Natural Science and Engineering Research Council of Canada for financial support through Grant A-5319. 相似文献
8.
In the present paper, we define the difference sequence space r
q
(p, Δ), which is defined as follows:
where r
q
(p) is the Riesz sequence space given by Altay and Basşar. We give some topological properties and compute the α-, β- duals of this space.
相似文献
9.
《Operations Research Letters》2014,42(1):16-20
We consider semi-infinite linear programs with countably many constraints indexed by the natural numbers. When the constraint space is the vector space of all real valued sequences, we show that the finite support (Haar) dual is equivalent to the algebraic Lagrangian dual of the linear program. This settles a question left open by Anderson and Nash (1987). This result implies that if there is a duality gap between the primal linear program and its finite support dual, then this duality gap cannot be closed by considering the larger space of dual variables that define the algebraic Lagrangian dual. However, if the constraint space corresponds to certain subspaces of all real-valued sequences, there may be a strictly positive duality gap with the finite support dual, but a zero duality gap with the algebraic Lagrangian dual. 相似文献
10.
Characteristic tilting modules and Ringel duals 总被引:6,自引:0,他引:6
XI Changchang 《中国科学A辑(英文版)》2000,43(11):1121-1130
The characteristic tilting modules of quasi-hereditary algebras which are dual extensions of directed monomial algebras are
explicitly constructed; and it is shown that the Ringel dual of the dual extension of an arbitrary hereditary algebra has
triangular decomposition and bipartite quiver. 相似文献