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Questions about the branch of algebra that deals with groups.

10 votes
Accepted

Classifying Space of a Group Extension

Yes. The principal bundles are the same and your guess that $BA$ is an abelian group is exactly right. A good reference for this story, and of Segal's result that David Roberts quotes, is Segal's pape …
Chris Schommer-Pries's user avatar
7 votes

Extension problem

The subtlety is in when two extensions are considered the same, in other words what are the morphisms of extension? There are different reasonable answers. For example a morphism could just be a morph …
Chris Schommer-Pries's user avatar