GO-空间乘积的子空间仿紧性的充分必要条件

我们知道,GO-空间乘积的子空间不一定仿紧.在2000年,数学家N.Kemoto,K.Tamano和Y.Yajima证明了两个特殊的GO-空间-序数乘积子空间的仿紧性的一个充分必要条件.把这个定理进行了推广,到了两个一般的GO-空间乘积的任意子空间仿紧性的一个充分必要条件.     

拟仿紧性与乘积空间

本文证明了在V=L假定下,所有正规局部紧拟仿紧空间是仿紧的.并证明了正则拟仿紧性在有限对一闭映射下是逆保持的.还研究了狭义拟仿紧性的有限乘积和逆极限定理.     

L-拓扑空间中的W-仿紧性

利用α-局部有限族在L-拓扑空间中定义了一种新型强F仿紧性--W-仿紧性,证明了这种仿紧性具有一些好的性质,比如L-good extension,闭遗传,弱同胚不变性,强F紧集与W-仿紧集的乘积是W-仿紧集.并同时证明了W-仿紧性可以增强分离性,最后讨论了W-仿紧性与其他仿紧性之间的关系.     

关于遗传可遮和遗传σ-亚紧可数乘积的注记

证明了在逆序列的情形下,可遮空间、强可遮空间在假设X是可数仿紧空间的条件下可被其极限空间保持,进一步证明了遗传可遮,遗传强可遮及遗传σ-亚紧性在无需对投射及极限空间X做任何假设的情况下即可被其逆极限空间保持.作为上述两个结果的应用,分别给出了两个相关的可数Tychonoff乘积定理.     

拟仿紧性与乘积空间

本文证明了在V=L假定下,所有正规局部紧拟仿紧空间是仿紧的．并证明了正则拟仿紧性在有限 对一闭映射下是逆保持的．还研究了狭义拟仿紧性的有限乘积和逆极限定理．     

不可数多个GO-空间乘积的k-仿紧性

证明了不可数多个GO-空间的乘积是k-仿紧空间(相似文献   

关于三角范畴中由对象决定的态射的一个注记

由对象决定的态射的概念由Auslander提出.之后Krause证明了在含有Serre函子的Hom-有限的Krull-Schmidt R-线性三角范畴T中,任意态射f的决定子都存在.本文对该结论做了一个补充,给出了T中任意态射f的极小决定子D(f)的具体形式.     

GO-空间乘积的子空间的广义仿紧性

20 0 0年 ,数学家 N .Kemoto,K.Tam ano和 Y.Yajima证明了两个特殊的 GO-空间——序数乘积子空间的亚紧性 ,screenability,弱 submetalindelof性是等价的 .本文把这个命题推广到了两个一般的 GO-空间乘积的任意子空间上 ,证明了它们仍然是等价的 .     

σ按点族正规性,σ亚紧性和σ按点有限基

<正> 对仿紧空间和拓扑空间度量化问题的研究引出了两个重要概念:族正规性(Collec-tionwise normality,简记为CWN)和亚紧性(metacompactness).Michael于1955年证明了空间X仿紧的充要条件为X是CWN和亚紧的.沿着弱化CWN和亚紧性的方向,     

LF内部空间的仿紧性

在LF内部空间中,引入了Q-内部域、α-Q-内部族等概念,并以此定义了F紧集和F仿紧集,给出了它们的特征刻画。证明了F紧集是F仿紧集,F仿紧性是F可乘性。     

Nichtdifferenzierbare Morphismen differenzierbarer Räume

It is known ([4]) that under certain general conditions formal morphisms of differentiable spaces are differentiable. In this paper we show that these conditions are essentially necessary. Especially we establish the existence of formal, not differentiable morphisms of differentiable algebras. This solves a problem due to B. Malgrange ([1]).     

Factorizable inverse monoids

Factorizable inverse monoids constitute the algebraic theory of those partial symmetries which are restrictions of automorphisms; the formal definition is that each element is the product of an idempotent and an invertible. This class of monoids has theoretical significance, and includes concrete instances which are important in various contexts. This survey is organised around the idea of group acts on semilattices and contains a large range of examples. Topics also include methods for construction of factorizable inverse monoids, and aspects of their inner structure, morphisms, and presentations.     

Preunits and weak crossed products

Using the notion of a preunit and the properties of idempotent morphisms, we give a general notion of a crossed product of an algebra A and an object V both living in a monoidal category C. We endow A⊗V with a multiplication and an idempotent morphism, whose image inherits the multiplication. Sufficient conditions for these multiplications to be associative are given. If the product on A⊗V has a preunit, the related idempotent is given in terms of the preunit, and its image has an algebra structure. A characterization of crossed products with preunit is given, and it is used to recover classical examples of crossed products and to study crossed products in weak contexts. Finally crossed products of an algebra by a weak bialgebra are recovered using this theory.     

On the push-forwards for motivic cohomology theories with invertible stable Hopf element

We present a geometric construction of push-forward maps along projective morphisms for cohomology theories representable in the stable motivic homotopy category assuming that the element corresponding to the stable Hopf map is inverted in the coefficient ring of the theory. The construction is parallel to the one given by Nenashev for derived Witt groups. Along the way we introduce cohomology groups twisted by a formal difference of vector bundles as cohomology groups of a certain Thom space and compute twisted cohomology groups of projective spaces.     

REDUCIBILITY IN SOME CATEGORIES OF PARTIAL RECURSIVE OPERATORS

We consider two categories with one object, namely the set of all partial functions of one variable from the set of natural numbers into itself; the morphisms are the partial recursive operators in one case, and certain continuous partial mappings in the other case. We show that these categories are recursion categories and we characterize the domains and the complete domains. Some observations are made on a notion of reducibility obtained by using the total morphisms of these categories, and, subsequently, the general recursive operators.     

Quantale中的模糊滤子

在Quantale中引入模糊滤子的概念,研究了它的一系列性质,得到了若干等价刻画,讨论了Quantale中滤子和模糊滤子之间的相互确定关系,证明了Quantale态射既保模糊滤子又反射模糊滤子。给出了模糊滤子在Quantale态射下的像的具体结构。     

模糊形式背景下的类近似算子

分别在形式背景和模糊形式背景下定义类下近似算子和类模糊下近似算子,并研究它们的性质.证明这两种算子分剐等价于形式背景和模糊形式背景下的*算子和模糊*算子.进一步给出类下近似算子与类模糊下近似算子的公理刺画.最后,对偶地讨论类上近似算子和类模糊上近似算子的定义和性质.     

Tensor products of contexts and complete lattices

Although the categoryCLC of complete lattices and complete homomorphisms does not possess arbitrary coproducts, we show that the tensor product introduced by Wille has the universal property of coproducts for so-called distributing families of morphisms (and only for these). As every family of morphisms into a completely distributive lattice is distributing, this includes the known fact that in the category of completely distributive lattices, arbitrary coproducts exist and coincide with the tensor products. Since the definition of tensor products is based on the notion of contexts and their concept lattices, many results on tensor products extend from complete lattices to contexts. Thus we introduce two kinds of tensor products for arbitrary families of contexts, a partial and a complete one, and establish universal properties of these tensor products.Presented by B. Jonsson.     

Local structure theorems for smooth maps of formal schemes

We continue our study on infinitesimal lifting properties of maps between locally noetherian formal schemes started in [L. Alonso Tarrío, A. Jeremías López, M. Pérez Rodríguez, Infinitesimal lifting and Jacobi criterion for smoothness on formal schemes, Comm. Alg. 35 (2007) 1341-1367]. In this paper, we focus on some properties which arise specifically in the formal context. In this vein, we make a detailed study of the relationship between the infinitesimal lifting properties of a morphism of formal schemes and those of the corresponding maps of usual schemes associated to the directed systems that define the corresponding formal schemes. Among our main results, we obtain the characterization of completion morphisms as pseudo-closed immersions that are flat. Also, the local structure of smooth and étale morphisms between locally noetherian formal schemes is described: the former factors locally as a completion morphism followed by a smooth adic morphism and the latter as a completion morphism followed by an étale adic morphism.     

Reflection Ideals and mappings between generic submanifolds in complex space

Results on finite determination and convergence of formal mappings between smooth generic submanifolds in ℂ ^N are established in this article. The finite determination result gibes sufficient conditions to guarantee that a formal map is uniquely determined by its jet, of a preassigned order, at a point. Convergence of formal mappings for real-analytic generic submanifolds under appropriate assumptions is proved, and natural geometric conditions are given to assure that if two germs of such submanifolds are formally equivalent, then, they are necessarily biholomorphically equivalent. It is also shown that if two real-algebraic hypersurfaces in ℂ ^N are biholomorphically equivalent, then, they are algebraically equivalent. All the results are first proved in the more general context of “reflection ideals” associated to formal mappings between formal as well as real-analytic and real-algebraic manifolds.