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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.

7 votes

Group cohomology version of Deligne-Beilinson cohomology

Note that Deligne-Beilinson cohomology is not really a "topological cohomology" generalization of de Rham cohomology, it depends on additional analytic structure. So one would expect that some additio …
Matthias Wendt's user avatar
37 votes
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$H^4(BG,\mathbb Z)$ torsion free for $G$ a connected Lie group

I try to give an argument without spectral sequences, not sure if this can be considered non-computational though. At least, there is a non-computational syllabus: torsion classes in $H^4(BG,\mathbb{Z …
Matthias Wendt's user avatar