共查询到20条相似文献,搜索用时 31 毫秒
1.
Alex Chigogidze 《Proceedings of the American Mathematical Society》2001,129(10):2959-2963
We show that complemented subspaces of uncountable products of Banach spaces are products of complemented subspaces of countable subproducts.
2.
Let F and G be closed subspaces of the complex Hilbert space H, and U and V be closed subspaces of F and G, respectively. In this paper, using the technique of operator block, we present the necessary and sufficient conditions under which (U, V) is a pair of (strictly, non-degenerate) principal invariant subspaces for (F, G). 相似文献
3.
Eva Murtinová 《Czechoslovak Mathematical Journal》2004,54(3):807-815
Some constructions of spaces with/without dense subspaces satisfying stronger separation axioms are presented. 相似文献
4.
证明了一类次可分解算子的不变子空间格是丰富的,并举例说明存在Hilbert空间上的有界线性算子T,它有无穷多个不变子空间,但是它的不变子空间格Lat(T)不丰富. 相似文献
5.
We use the Weierstrass σ-function associated with a lattice in the complex plane to construct finite dimensional zero-based subspaces and quasi-invariant subspaces of given index in the Bargmann-Fock space. 相似文献
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7.
Darapaneni Narayana 《Proceedings of the American Mathematical Society》2006,134(4):1167-1172
We characterize finite-dimensional normed linear spaces as strongly proximinal subspaces in all their superspaces. A connection between upper Hausdorff semi-continuity of metric projection and finite dimensionality of subspace is given.
8.
Using the relation between subspaces of Banach spaces and quotients of their duals, we introduce the concept of colocality to give a new method that guarantees the existence of nontrivial twisted sums in which finite quotients play a major role (Theorem 1.7). An interesting point is that no restrictions are imposed on the quotients, only on the various subspaces. New examples of nontrivial twisted sums are given. 相似文献
9.
Let S be a pre-Hilbert space. We study quasi-splitting subspaces of S and compare the class of such subspaces, denoted by Eq(S), with that of splitting subspaces E(S). In [D. Buhagiar, E. Chetcuti, Quasi splitting subspaces in a pre-Hilbert space, Math. Nachr. 280 (5-6) (2007) 479-484] it is proved that if S has a non-zero finite codimension in its completion, then Eq(S)≠E(S). In the present paper it is shown that if S has a total orthonormal system, then Eq(S)=E(S) implies completeness of S. In view of this result, it is natural to study the problem of the existence of a total orthonormal system in a pre-Hilbert space. In particular, it is proved that if every algebraic complement of S in its completion is separable, then S has a total orthonormal system. 相似文献
10.
A compact space Q similar to the compact space known as Alexandroff's double arrow space is constructed. It is shown that the real space C(Q) has no Chebyshev subspaces of codimension >1, but the complex space C(Q) has such subspaces. 相似文献
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In this paper, we shall introduce and characterize simultaneous quasi-Chebyshev (and weakly-Chebyshev) subspaces of normed spaces with respect to a bounded set S by using elements of the dual space. 相似文献
13.
设Fq(n)是Fq上的n维正交空间,设P是任一个给定的m维全奇异子空间.计算了F(qn)中满足dim(P∩Q)=i的r维全奇异子空间Q的个数,给出了用子空间构作认证码的例子. 相似文献
14.
刘明学 《应用泛函分析学报》2003,5(1):79-81
得到了关于序列次可分解算子的一个不变子空间定理,推广了H.Mohebi和M.Rajiabalipour在1994年得到的一个不变子空间定理,并且举例说明存在l2上的有界线性算子T。它有无穷多个变子空间,但是它的不变子空间格Lat(T)不丰富。 相似文献
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16.
Darapaneni Narayana 《Journal of Mathematical Analysis and Applications》2006,321(1):193-197
We give simple proofs of some results of Mohebi [H. Mohebi, On quasi-Chebyshev subspaces of Banach spaces, J. Approx. Theory 107 (2000) 87-95] on quasi-Chebyshev subspaces. 相似文献
17.
Sofiya Ostrovska 《数学学报(英文版)》2015,31(5):767-771
Norming subspaces are studied widely in the duality theory of Banach spaces. These subspaces are applied to the Borel and Baire classifications of the inverse operators. The main result of this article asserts that the dual of a Banach space X contains a norming subspace isomorphic to l1 provided that the following two conditions are satisfied: (1) X* contains a subspace isomorphic to l1; and (2) X* contains a separable norming subspace. 相似文献
18.
The local reconstruction from samples is one of the most desirable properties for many applications in signal processing. Local sampling is practically useful since we need only to consider a signal on a bounded interval and computer can only process finite samples. However, the local sampling and reconstruction problem has not been given as much attention. Most of known results concern global sampling and reconstruction. There are only a few results about local sampling and reconstruction in spline subspaces. In this article, we study local sampling and reconstruction in general shift-invariant spaces and multiple generated shift-invariant spaces with compactly supported generators. Then we give several applications in spline subspaces and multiple generated spline subspaces. 相似文献
19.
This paper provides some new families of symmetric association schemes based on maximal totally isotropic subspaces in (singular) pseudo-symplectic spaces. All intersection numbers of these schemes are computed. 相似文献
20.
As a counterpart to best approximation in normed linear spaces, the best coapproximation was introduced by Franchetti and
Furi. In this paper, we shall consider the relation between coproximinality M in X and L
p
(S,M) in L
p
(S,X). Finally we give some results in cochebyshev subspaces and additional subspaces. 相似文献