Eigenvalue completions by affine varieties

In this paper we provide new necessary and sufficient conditions for a general class of eigenvalue completion problems.

     

A Link Between Two Connectedness Notions

The composition of two previously introduced Galois connections is used to provide a wider perspective on the Clementino–Tholen connectedness versus separation Galois connection. Moreover, a link between this and Castellini's connectedness–disconnectednes Galois connection is also presented.     

加法范畴中态射的双积与群逆

研究了加法范畴上具有满单分解的态射的群逆,通过构造双积给出了群逆存在的充要条件及表达式.     

A simple remark on a flat projective morphism with a Calabi-Yau fiber

If a K3 surface is a fiber of a flat projective morphisms over a connected noetherian scheme over the complex number field,then any smooth connected fiber is also a K3 surface.Observing this,Professor Nam-Hoon Lee asked if the same is true for higher dimensional Calabi-Yau fibers.We shall give an explicit negative answer to his question in each dimension greater than or equal to three as well as a proof of his initial observation.     

What is a Quotient Map with Respect to a Closure Operator?

It is shown that there is no good answer to the question of the title, even if we restrict our attention to S et-based topological categories. Although very closely related, neither the natural notion of c-finality (designed in total analogy to c-initiality) nor the notion of c-quotient (modelled after the behaviour of topological quotient maps) provide universally satisfactory concepts. More dramatically, in the category T op with its natural Kuratowski closure operator k, the class of k-final maps cannot be described as the class of c-quotient maps for any closure operator c, and the class of k-quotients cannot be described as the class of c-final maps for any c. We also discuss the behaviour of c-final maps under crossing with an identity map, as in Whitehead's Theorem. In T op, this gives a new stability theorem for hereditary quotient maps.     

Factorization properties of birational mappings

We analyse birational mappings generated by transformations on q × q matrices which correspond respectively to two kinds of transformations: the matrix inversion and a permutation of the entries of the q × q matrix. Remarkable factorization properties emerge for quite general involutive permutations.

It is shown that factorization properties do exist, even for birational transformations associated with noninvolutive permutations of entries of q × q matrices, and even for more general transformation which are rational transformations but no longer birational. The existence of factorization relations independent of q, the size of the matrices, is underlined.

The relations between the polynomial growth of the complexity of the iterations, the existence of recursions in a single variable and the integrability of the mappings, are sketched for the permutations yielding these properties.

All these results show that permutations of the entries of the matrix yielding factorization properties are not so rare. In contrast, the occurrence of recursions in a single variable, or of the polynomial growth of the complexity are, of course, less frequent but not completely exceptional.     

6-CANONICAL MAPS OFNONSINGULAR MINIMAL 3-FOLDS

６－ＣＡＮＯＮＩＣＡＬＭＡＰＳＯＦＮＯＮＳＩＮＧＵＬＡＲＭＩＮＩＭＡＬ３－ＦＯＬＤＳ￥ＣＨＥＮＭＥＮＧＡｂｓｔｒａｃｔ：Ｔｈｅａｉｍｏｆｔｈｉｓｐａｐｅｒｉｓｔｏｓｔｕｄｙ６－ｃａｎｏｎｉｃａｌｓｙｓｔｅｍｏｆａｎｏｎｓｉｎｇｕｌａｒｍｉｎｉｍａｌ３...     

Abel范畴中态射乘积诱导的短正合列及其应用

本文给出了Ａｂｅｌ范畴中态射乘积αβγ诱导的短正合列的立体交换图。其中共有７个３×３平面，３０条线。每一条线（两端的零对象省略）都是一个短正合列．这些短正合列用到ｐ－除环上的矩阵，可以导出一系列矩阵秩的恒等式，它不仅推广了域上矩阵秩的结果，还能得到一些新的关系式．     

Separated and Connected Maps

Using on the one hand closure operators in the sense of Dikranjan and Giuli and on the other hand left- and right-constant subcategories in the sense of Herrlich, Preuß, Arhangel'skii and Wiegandt, we apply two categorical concepts of connectedness and separation/disconnectedness to comma categories in order to introduce these notions for morphisms of a category and to study their factorization behaviour. While at the object level in categories with enough points the first approach exceeds the second considerably, as far as generality is concerned, the two approaches become quite distinct at the morphism level. In fact, left- and right-constant subcategories lead to a straight generalization of Collins' concordant and dissonant maps in the category of topological spaces. By contrast, closure operators are neither able to describe these types of maps in , nor the more classical monotone and light maps of Eilenberg and Whyburn, although they give all sorts of interesting and closely related types of maps. As a by-product we obtain a negative solution to the ten-year-old problem whether the Giuli–Huek Diagonal Theorem holds true in every decent category, and exhibit a counter-example in the category of topological spaces over the 1-sphere.     

关于具有泛分解态射的加权Moore-Penrose逆

给出了预加法范畴中具有泛分解态射的加权Moore-Penrose逆存在的充要条件及其表达式,推广了具有泛分解的态射的Moore-Penrose逆的相应结果.