4 papers
A characterization of complex projective space via the Calabi curvature operator
Hasan M. El-Hasan, Xiaolong Li, Jan Nienhaus +3
We prove a Tachibana-type result for Kähler-Einstein manifolds isolating complex projective space based on its Calabi curvature operator. The proof uses a new Bochner formula expre…
On Hopf's conjecture and positive second intermediate Ricci curvature
Lee Kennard, Lawrence Mouillé, Jan Nienhaus
Hopf conjectured that even-dimensional closed Riemannian manifolds with positive sectional curvature have positive Euler characteristic. The conclusion of the conjecture is known t…
Vanishing theorems for Hodge numbers and the Calabi curvature operator
Kyle Broder, Jan Nienhaus, Peter Petersen +2
It is shown that a compact -dimensional Kähler manifold with -positive Calabi curvature operator has the rational cohomology of complex projective space. For even…
Einstein metrics on the Ten-Sphere
Jan Nienhaus, Matthias Wink
We prove the existence of three non-round, non-isometric Einstein metrics with positive scalar curvature on the sphere Previously, the only even-dimensional spheres known…