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| | [No title] (Site not responding. Last check: 2007-10-08) |
 | | By definition, a principal bundle with group S1 has fibre S1, structure group S1, with the group S1 acting on the fiber by left multiplication. |
 | | In case you meant this, note that it is also true that if the base space is orientable, the total space of any principal S1 bundle will also be orientable, and here is the proof: at every point in the n-dimensional base space M, we have an n-form \omega that defines the orientation. |
 | | It is straightforward to check that this is a fibre bundle with fibre S1 (and structure group Z/2, in case you care). |
| www.lehigh.edu /~dmd1/ki97.txt (605 words) |
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