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Jan
30
awarded  Nice Question
Oct
24
answered Inference of an identity in Grassmann algebra.
Oct
5
revised Radius of convergence of a power series - how can I be sure $\lim \frac{a_{n+1}}{a_n}$ exists?
added explanation to inner limit
Oct
5
answered Radius of convergence of a power series - how can I be sure $\lim \frac{a_{n+1}}{a_n}$ exists?
Sep
27
awarded  Popular Question
Aug
12
revised Characters appearing naturally in arithmetic functions
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Aug
12
asked Characters appearing naturally in arithmetic functions
Aug
12
revised From 4 squares to 2 squares
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Aug
12
asked From 4 squares to 2 squares
Aug
9
comment A Combinatorial Proof of Dixon's Identity
Thanks, @darijgrinberg! It's a good article to display the diversity of techniques for proving combinatorial identites.
Jun
20
revised Number of solutions of $x^2_1+\dots+x^2_n=0,$ $x_i\in \Bbb{F}_q.$
fixed sign mistakes
Jun
3
comment From Tilings To Groups
(cont.) To get full understanding one should see what Gromov's motivation was for the word-hyperbolic definition, and read his books. I guess the theorem you mentioned will make an appearance there.
Jun
3
comment From Tilings To Groups
Thanks. I'll go on reading about this theorem (does it have a name, btw?). I've already seen the notion of quasi-isometry and its relation to Cayley graphs (actually, the primer also includes the $\delta$ definition of hyperbolicity). The more I read, the more I understand that the word-hyperbolic def. is useful for proving some theorems (say, "Density 1/2" of Gromov, which I recommend reading), but is not the most intuitive and especially not the most geometric.
Jun
3
accepted From Tilings To Groups
Jun
3
revised From Tilings To Groups
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Jun
3
revised From Tilings To Groups
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Jun
3
asked From Tilings To Groups
May
11
awarded  Nice Answer
May
1
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Apr
11
comment Can someone please explain the Riemann Hypothesis to me… in English?
Can anyone provide a free link to the first linked paper?