Abstract:
Let $H$ be an infinite hyperbolic group with Kazhdan property $(T)$ and let $\varkappa(H,X)$ denote the Kazhdan constant of $H$ with respect to a generating set $X$. We prove that $\inf_{X}\varkappa(H,X)=0$, where the
infimum is taken over all finite generating sets of $H$. In particular, this gives an answer to a Lubotzky question.
Keywords:Kazhdan property (T), hyperbolic group, left regular representation, amenable group.