Alon Amit
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 Mar 19 revised What are the worst notations, in your opinion ? added 24 characters in body Mar 19 comment What are the worst notations, in your opinion ? @Qiaochu: I'm really only talking about the interior case. It's then that the \osum is the same subspace as the sum but with the implied additional condition on the subspaces. Mar 19 comment how slow can the dimension of a product set grow? So the circle S^1 has dimension 2 in your sense? If so, I don't know if this has a name but I certainly wouldn't recommend "dimension". Mar 19 comment What are the worst notations, in your opinion ? @Francois: Sheesh, of course. Sorry. Fixed. Mar 19 revised What are the worst notations, in your opinion ? deleted 4 characters in body; added 11 characters in body Mar 18 answered What are the worst notations, in your opinion ? Mar 17 comment Fundamental groups of noncompact surfaces If I had been faster I would have proposed the same reference so you wouldn't have had to advertise your own book. I'm a fan :-) Mar 16 comment Properties of Graphs with an eigenvalue of -1 (adjacency matrix)? If G->B is a covering map (in the topological sense), then G inherits all the eigenvalues of B (just choose an eigenfunction that is uniform on the fibers). So, for instance, any graph which covers K_n for any n has -1 as an eigenvalue. The cycle of length 3k covers the triangle, which is another way to explain Kevin's example. Mar 16 awarded Nice Answer Mar 16 awarded Popular Question Mar 14 awarded Enlightened Mar 14 awarded Nice Answer Mar 12 comment Books you would like to see translated into English. That's +10 from me, too. Mar 10 answered A historical question: Hurwitz, Luroth, Clebsch, and the connectedness of M_g Mar 9 revised Why are the sporadic simple groups HUGE? added 2 characters in body Mar 9 comment If $2^x$and $3^x$ are integers, must $x$ be as well? This answer was given by Gerry. I just added the link to Wikipedia. Mar 9 revised If $2^x$and $3^x$ are integers, must $x$ be as well? Added wikipedia link Mar 9 comment If $2^x$and $3^x$ are integers, must $x$ be as well? Very interesting! Just to make sure I understand - does this generalize the "n^x for all n" version only, or can it be applied to "2,3,5" and "2,3" as well? Mar 9 accepted If $2^x$and $3^x$ are integers, must $x$ be as well? Mar 9 comment If $2^x$and $3^x$ are integers, must $x$ be as well? @jef: the best hint I can think of is "calculus of differences".