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| | [No title] (Site not responding. Last check: 2007-10-23) |
 | | That space, which I described as a quotient space of the disc, was really the result of taking a circle and glomming a disc onto it in such a way that the edge of the disc wrapped around the circle 5 times. |
 | | As Rusin points out, K(G,n) is cool because it's a space that knows all about n-dimensional homology with coefficients in the group G. To figure out H_n(X,G) for any space X, we just form the set of homotopy equivalence classes of maps from X to K(G,n), usually written [X,K(G,n)]. |
 | | The wedge product is the coproduct in the category of pointed spaces (spaces with one point declared to be a "basepoint") This is simply the coproduct in the category of spaces (or sets), namely disjoint union, modulo an equivalence relation that declares the two basepoints equivalent. |
| www.mat.niu.edu /~rusin/known-math/94/holes (2375 words) |
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