Complete spacelike hypersurfaces with constant mean curvature in \(-\mathbb R\times \mathbb H^n\)
By applying the Omori-Yau generalized maximum principle for complete Riemannian manifolds, the authors prove the following Bernstein-type results: Theorem 1.1. Let \(\psi:\Sigma^n\to-\mathbb{R}\times\mathbb{H}^n\) be a complete space-like hypersurface with constant mean curvature \(H\). If the height function \(h\) of \(\Sigma^n\) satisfies, for some constant \(0<\alpha<1\), \(\displaystyle|\nabla h|^2\leq\frac{n\alpha}{n-1}H^2\), then \(\Sigma^n\) is a slice. Theorem 1.2. Let \(\psi:\Sigma^n\to-\mathbb{R}\times\mathbb{H}^n\) be a complete space-like hypersurface with constant mean curvature \(H\), and the 2-mean curvature \(H_2\) bounded from below. If the height function \(h\) of \(\Sigma^n\) satisfies, for some constant \(0<\alpha<1\), \(\displaystyle |\nabla h|^2\leq\frac{\alpha}{n-1}|A|^2\), where \(|A|^2\) denotes the squared norm of the shape operator \(A\), then \(\Sigma^n\) is a slice. The first author has given some examples of complete and non-complete entire maximal graphs in \(-\mathbb{R}\times\mathbb{H}^2\) which are not slices [see, Differ. Geom. Appl. 26, No.~4, 456--462 (2008; Zbl 1147.53047)].
scientific article; zbMATH DE number 5712602
scientific article