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The classifying space BG of a group G classifies principal G-bundles, in that homotopy classes of maps [X, BG] are naturally identified with isomorphism classes of principal G-bundles P ⭢ X.

3 votes
2 answers
338 views

Is this true of the frame bundle $\operatorname{Fr}(M)$?

On an orientable (Riemannian) $n$-manifold $M$, with orthonormal frame bundle $\operatorname{Fr}(M)$, we have that the tangent bundle classifying map $\tau_M : M \to B{\operatorname O(n)}$ lifts to $B …
Arnav Das's user avatar
3 votes
1 answer
230 views

Do the two orientations on an orientable manifold $M$ witness the same lifts of $\tau_M: M \...

For an orientable $n$-manifold $M$ and its (orthonormal) frame bundle classifying map $\tau_M : M \to BO(n)$, we have a lift diagram of the following sort: There are two orientations on $M$. Is it ev …
Arnav Das's user avatar
8 votes
1 answer
398 views

Reduction of structure group and classifying spaces

Let $H, G$ be topological groups and $\phi : H \to G$ a group homomorphism. Let $M$ be a paracompact topological space. For any principal $G$-bundle $P \to M$, a reduction (or sometimes 'lift') of its …
Arnav Das's user avatar