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3 votes
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Property $(T)$ for $\mathrm{SL}_2(\mathbb{Z}) \ltimes \mathbb{Z}^2$

(This is in part a request for references and in part a somewhat pedagogical question.) I gave a course on expanders seven years ago, and I am giving a course on expanders again now. We will soon do ...
H A Helfgott's user avatar
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3 votes
0 answers
357 views

What about a Cayley n-complex for n>2?

Let $G$ be a finitely presented group. The Cayley graph of the finite generating set is a $1$-complex where the $0$-cells are the elements of $G$ and the $1$-cells are given by the generators (...
Sebastien Palcoux's user avatar
2 votes
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117 views

Bruhat-Tits tree as Cayley graph of free group

$\DeclareMathOperator\BT{BT}\DeclareMathOperator\GL{GL}$Let $p > 2$ be a prime and $n = \frac{p + 1}{2}$. We can identify the vertices of Bruhat-Tits tree $\BT(\mathbb Q_p)$ with the elements in ...
fyo's user avatar
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