Notes on periodic elements of Garside groups

Let $G$ be a Garside group with Garside element $\mathrm{\Delta }$. An element $g$ in $G$ is said to be \emph{periodic} if some power of $g$ lies in the cyclic group generated by $\mathrm{\Delta }$. This paper shows the following. (i) The periodicity of an element does not depend on the choice of a particular Garside structure if and only if the center of $G$ is cyclic. (ii) If $g^k={\mathrm{\Delta }}^{ka}$ for some nonzero integer $k$, then $g$ is conjugate to ${\mathrm{\Delta }}^a$. (iii) Every finite subgroup of the quotient group $G\mathrm{/}<{\mathrm{\Delta }}^m>$ is cyclic, where ${\mathrm{\Delta }}^m$ is the minimal positive central power of $\mathrm{\Delta }$.