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A222010
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Dimensions of spheres that admit continuous multiplications with unit element.
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1
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OFFSET
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0,3
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COMMENTS
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Adams's (1960) Hopf invariant one theorem states that S^0, S^1, S^3, S^7 are the only spheres that are H-spaces, i.e., that admit continuous multiplications with unit element.
This is related to the fact that nontrivial cross products only exist in vector spaces of 3 or 7 dimensions. [Jonathan Vos Post, Feb 09 2013]
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LINKS
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FORMULA
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a(n) = 2^n - 1 for n = 0, 1, 2, 3.
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EXAMPLE
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0, 1, 3, 7 are members because multiplications on S^0, S^1, S^3, S^7 are defined by regarding them as the unit spheres in the real, complex, quaternion, and Cayley numbers, respectively.
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CROSSREFS
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KEYWORD
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nonn,fini,full,nice
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AUTHOR
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STATUS
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approved
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