Nombre de classes de conjugaison delements dordre fini dans les groupes de Brown-Thompson


Abstract in English

We extend a result of Matucci on the number of conjugacy classes of finite order elements in the Thompson group $T$. According to Liousse, if $ gcd(m-1,q)$ is not a divisor of $r$ then there does not exist element of order $q$ in the Brown-Thompson group $T_{r,m}$. We show that if $ gcd(m-1,q)$ is a divisor of $r$ then there are exactly $varphi(q). gcd(m-1,q)$ conjugacy classes of elements of order $q$ in $T_{r,m}$, where $varphi$ is the Euler function phi. As a corollary, we obtain that the Thompson group $T$ is isomorphic to none of the groups $T_{r,m}$, for $m ot=2$ and any morphism from $T$ into $T_{r,m}$, with $m ot=2$ and $r ot= 0$ $mod (m-1)$, is trivial.

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