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seen Oct 19 '11 at 12:56

Jul
2
awarded  Curious
Nov
10
awarded  Popular Question
Oct
13
revised $S^n \backslash S^m $ homotopy equivalent to $ S^{n-m-1} $
added 69 characters in body
Oct
13
revised $S^n \backslash S^m $ homotopy equivalent to $ S^{n-m-1} $
added 42 characters in body
Oct
13
asked $S^n \backslash S^m $ homotopy equivalent to $ S^{n-m-1} $
Oct
13
asked Homotopy equivalence definition
Oct
13
asked Which of the letters of the alphabet are contractible?
Oct
11
comment Basic property of homotopy
Great, that makes sense. I'll prove that now, and adopt this notation for the future. Thanks a lot
Oct
11
comment Basic property of homotopy
Is that the identity on $X$ or on $I$? I've never seen this notation before. Thanks
Oct
11
revised Basic property of homotopy
edited body
Oct
11
asked Basic property of homotopy
Oct
10
accepted Antipodal map on $ S^n $ homotopic to identity map if $n$ is odd
Oct
7
comment Antipodal map on $ S^n $ homotopic to identity map if $n$ is odd
Thanks, but I don't understand what you mean by "Notice that, since we had to rely on complex numbers, this does not work for even spheres."
Oct
7
asked Antipodal map on $ S^n $ homotopic to identity map if $n$ is odd
Aug
26
comment n-ary derived operation in universal algebra
Thanks - I'd assumed it was standard notation.
Aug
26
revised Menger's Theorem (updated)
edited title
Aug
26
revised Menger's Theorem (updated)
added 365 characters in body
Aug
26
comment Menger's Theorem (updated)
I think I understand now, actually. We might be tempted to say "suppose all $a$-$b$ separators have size $\geq k$. Find a maximum-sized family of independent paths, and choose a point from each of these paths. Then the set of these points is an $a$-$b$ separator, and so there must be at least $k$ paths in the family". But the part in italics isn't necessarily true. Take, for example, a hexagon with one diagonal and have $a$ and $b$ one vertex clockwise from the start of the diagonal at each end.
Aug
26
asked Menger's Theorem (updated)
Aug
26
comment n-ary derived operation in universal algebra
What are the $ x_i$?