共查询到20条相似文献,搜索用时 93 毫秒
1.
Bernardo Cascales Antonio J. Guirao Vladimir Kadets Mariia Soloviova 《Journal of Functional Analysis》2018,274(3):863-888
The Bishop–Phelps–Bollobás property deals with simultaneous approximation of an operator T and a vector x at which T nearly attains its norm by an operator and a vector , respectively, such that attains its norm at . In this note we extend the already known results about the Bishop–Phelps–Bollobás property for Asplund operators to a wider class of Banach spaces and to a wider class of operators. Instead of proving a BPB-type theorem for each space separately we isolate two main notions: Γ-flat operators and Banach spaces with structure. In particular, we prove a general BPB-type theorem for Γ-flat operators acting to a space with structure and show that uniform algebras and spaces with the property β have structure. We also study the stability of the structure under some natural Banach space theory operations. As a consequence, we discover many new examples of spaces Y such that the Bishop–Phelps–Bollobás property for Asplund operators is valid for all pairs of the form (). 相似文献
2.
3.
Denis S. Krotov 《Discrete Mathematics》2017,340(10):2559-2572
An extended -perfect trade is a pair of two disjoint binary distance- even-weight codes such that the set of words at distance from coincides with the set of words at distance from . Such trade is called primary if any pair of proper subsets of and is not a trade. Using a computer-aided approach, we classify nonequivalent primary extended -perfect trades of length , constant-weight extended -perfect trades of length , and Steiner trades derived from them. In particular, all Steiner trades with parameters are classified. 相似文献
4.
5.
Let and denote the maximum degree and the Laplacian spectral radius of a tree , respectively. In this paper we prove that for two trees and on vertices, if and , then , and the bound “” is the best possible. We also prove that for two trees and on vertices with perfect matchings, if and , then . 相似文献
6.
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
7.
We generalize results concerning -semigroups on Banach lattices to a setting of ordered Banach spaces. We prove that the generator of a disjointness preserving -semigroup is local. Some basic properties of local operators are also given. We investigate cases where local operators generate local -semigroups, by using Taylor series or Yosida approximations. As norms we consider regular norms and show that bands are closed with respect to such norms. Our proofs rely on the theory of embedding pre-Riesz spaces in vector lattices and on corresponding extensions of regular norms. 相似文献
8.
9.
For bipartite graphs , the bipartite Ramsey number is the least positive integer so that any coloring of the edges of with colors will result in a copy of in the th color for some . In this paper, our main focus will be to bound the following numbers: and for all for and for Furthermore, we will also show that these mentioned bounds are generally better than the bounds obtained by using the best known Zarankiewicz-type result. 相似文献
11.
12.
13.
《佛山科学技术学院》2014,6(1):115-131
We point out that the product of two fuzzy closed sets of smooth fuzzy topological spaces need not be fuzzy closed with respect to the the existing notion of product smooth fuzzy topology. To get this property, we introduce a new suitable product smooth fuzzy topology. We investigate whether and are weakly smooth fuzzy continuity whenever , , and are weakly smooth fuzzy continuous. Using this new product smooth fuzzy topology, we define smooth fuzzy perfect mapping and prove that composition of two smooth fuzzy perfect mappings is smooth fuzzy perfect under some additional conditions. We also introduce two new notions of compactness called -compactness and --compactness; and discuss the compactness of the image of a -compact set (--compact set) under a weakly smooth fuzzy continuous function (-weakly smooth fuzzy continuous function). 相似文献
14.
15.
16.
Anuj Jakhar Sudesh K. Khanduja Neeraj Sangwan 《Journal of Pure and Applied Algebra》2018,222(11):3560-3565
It is well known that if are algebraic number fields with coprime discriminants, then the composite ring is integrally closed and are linearly disjoint over the field of rationals, being the ring of algebraic integers of . In an attempt to prove the converse of the above result, in this paper we prove that if are finite separable extensions of a valued field of arbitrary rank which are linearly disjoint over and if the integral closure of the valuation ring of v in is a free -module for with integrally closed, then the discriminant of either or of is the unit ideal. We quickly deduce from this result that for algebraic number fields linearly disjoint over for which is integrally closed, the relative discriminants of and must be coprime. 相似文献
17.
18.
19.