THE CHEEGER CONSTANT OF AN ASYMPTOTICALLY LOCALLY HYPERBOLIC MANIFOLD AND THE YAMABE TYPE OF ITS CONFORMAL INFINITY

International audienceLet (M, g) be an (n + 1)-dimensional asymptotically locally hyperbolic (ALH) manifold with a conformal compactification whose conformal infinity is (∂M, [γ]). We will first observe that Ch(M, g) ≤ n, where Ch(M, g) is the Cheeger constant of M. We then prove that, if the Ricci curvature of M is bounded from below by −n and its scalar curvature approaches −n(n+1) fast enough at infinity, then Ch(M, g) = n if and only Y(∂M, [γ]) ≥ 0, where Y(∂M, [γ]) denotes the Yamabe invariant of the conformal infinity. This gives an answer to a question raised by J. Lee [L]