Optimal Sobolev inequalities in the hyperbolic space

Abstract: We find the optimal function norm on the left-hand side of the $m$th order Sobolev type inequality $|u|{Y(\mathbb{H}^n)} \leq C |\nabla_g^m u|{X(\mathbb{H}^n)}$ in the $n$-dimensional hyperbolic space $\mathbb{H}^n$, $1\leq m < n$. The optimal function norm in the inequality among all rearrangement-invariant function norms is completely characterized. A variety of concrete examples of optimal function norms in the inequality is provided. The examples include delicate limiting cases and, especially when $m\geq3$, seem to provide new, improved inequalities in these limiting cases.