On Hypersurfaces of ${\mathbb{H}}^2\times {\mathbb{H}}^2$

In this paper, we study hypersurfaces in ${\mathbb{H}}^2\times {\mathbb{H}}^2$. We first classify the hypersurfaces with constant principal curvatures and constant product angle function. Then, we classify homogeneous hypersurfaces and isoparametric hypersurfaces, respectively. Finally, we classify the hypersurfaces with at most two distinct constant principal curvatures, as well as those with three constant principal curvatures under some additional conditions.