摘要:

The doubly infinite diagram of exact sequences that an additive bifunctor T associates with a pair of short exact sequences can be regarded as a web diagram lying on the surface of a cylinder. The diagram has six diagonal sequences involving two graded derived functors that arise through the failure of T to preserve pull-backs respectively push-outs. In the case T = Hom(-,-) one of the diagonal sequences is equivalent to the bivariant Hom-Ext sequence studied by Pressmann [4].

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631569

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

We show that every map in the group G of self-homeomorphisms of the bisequence space can be approximated by homeomorphisms which “look like” the shift map and are expansive. By removing a certain open set of maps from G, we obtain a closed subspace M which contains all mixing maps. If φ · M then any shiftlike approximation to φ is topologically strong mixing. Thus the strong mixing expansive maps are dense in M. Further the weak mixing maps form a dense Gδ sets in M.

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631570

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

In this paper we investigate, for connection subcategoriesAof a topological categoryK, the concepts ofA-monotone quotients andA-light sources, and characterize (1) thoseA, which give rise to an (A-monotone quotient,A-light)- factorization structure onK, (2) those factorization structures (C,D) onK, which are light, i.e. of the form (A-monotone quotient,A-light) for suitableA. It turns out that light factorization structures are rather rare inTop, but abundant and well-behaved in categories with hereditary quotients.

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631571

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A categorical characterization of the categoryHausof Hausdorft topological spaces within the category Top of topological spaces is given. A notion of a Hausdorff nearness space is then introduced and it is proved that the resulting subcategoryHaus Nearof the categoryNearof nearness spaces fulfills exactly the same characterization as derived forHausinTop.Properties ofHaus Nearand relations to other important sub-categories ofNearare studied.

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631572

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A category Bch(X) of behaviours is introduced as a formalization of an external description of systems. It is show that the forgetful functor W: Bch(x) → K2is algebraic and that therefore Bch(x) has, and W preserves, whatever limits K has. Colimits and an image factorization system for Bch(X) are also investigated.

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631573

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631574

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

ISSN:1607-3606    

DOI:10.1080/16073606.1979.9631568

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor