Category Of Topological Spaces Article Index for
Category Of
Website Links For
Category
 

Information About

Category Of Topological Spaces




N.B. Some authors use the name Top for the category with Topological Manifold s as objects and continuous maps as morphisms.


TOP IS A CONCRETE CATEGORY


Like many categories, the category Top is a Concrete Category , meaning its objects are Set s with additional structure (i.e. topologies) and its morphisms are Function s preserving this structure. There is a natural Forgetful Functor
U

to the Category Of Sets which assigns to each topological space the underlying set and to each continuous map the underlying Function .


LIMITS AND COLIMITS


The category Top is both complete and cocomplete, which means that all small Limits and Colimit s exist in Top.

The forgetful functor ''U'' : Top → '''Set''' has a Left Adjoint which equips a given set with the Discrete Topology and a Right Adjoint which equips a given set with the Trivial Topology . This implies that the functor ''U'' is both limit-preserving and colimit-preserving, i.e. limits in Top are given by placing topologies on the corresponding limits in '''Set'''.

Examples of limits and colimits in Top include:



OTHER PROPERTIES




RELATIONSHIPS TO OTHER CATEGORIES




REFERENCES


  • Adámek, Jiří, Herrlich, Horst, & Strecker, George E.; (1990). ''Abstract and Concrete Categories'' (4.2MB PDF). Originally publ. John Wiley & Sons. ISBN 0-471-60922-6. (now free on-line edition).