Friday, 19 December 2008

at.algebraic topology - Fiber bundle = principal bundle + fiber?

This question is heavily related to this question.



Fix a sufficiently nice and connected topological space $B$ and let $FB$ be the category of fiber bundles over $B$. A morphism $f: (Eto B)to (E'to B)$ in this category is a map $Eto E'$ over $B$ and hence it maps fibers to fibers.



Edit: A fiber bundle $p:Eto B$ is a continuous map such that there exists a local trivialization. Since $B$ is nice and connected, all the fibers $p^{-1}(x)$ are isomorphic.



According to the very helpful answers here,



  • a fiber bundle over $B$ with fiber $F$ determines a $G=Aut(F)$-principal bundle together with (trivially) a left $G$-action on $F$ and

  • a $G$-principal bundle over $B$, where $G$ is an arbitrary topological group, together with a topological space $F$ and a left $G$-action on $F$ determines a fiber bundle over $B$ with fiber $F$.

Can one formulate this correspondence "categorically", i.e. is there an equivalence of the category $FB$ to a product (?) of two categories, one encoding the "glueing structure" (the principal bundle) and one encoding the "fiber information" (the space $F$ with the action)? (In particular, what should be the analogue to a morphism of fiber bundles?)



(Certainly is not possible to get such a description precisely like above because one have to fix the topological group $G$ to say what a space $F$ with a $G$-action is and conversely one have to fix a space $F$ to say what a $G=Aut(F)$-principal bundle is, but maybe there is a way to formulate this in general.)

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