De nouvelles formules de Weitzenböck pour des endomorphismes harmoniques. Applications géométriques
We construct biharmonic non-harmonic maps between Riemannian manifolds and by first making the ansatz that be a harmonic map and then deforming the metric on by to render biharmonic, where is a smooth function with gradient of constant norm on and . We construct new examples of biharmonic non-harmonic maps, and we characterize the biharmonicity of some curves on Riemannian manifolds.
We prove a universal inequality between the diastole, defined using a minimax process on the one-cycle space, and the area of closed Riemannian surfaces. Roughly speaking, we show that any closed Riemannian surface can be swept out by a family of multi-loops whose lengths are bounded in terms of the area of the surface. This diastolic inequality, which relies on an upper bound on Cheeger’s constant, yields an effective process to find short closed geodesics on the two-sphere, for instance. We deduce...
Groping our way toward a theory of singular spaces with positive scalar curvatures we look at the Dirac operator and a generalized Plateau problem in Riemannian manifolds with corners. Using these, we prove that the set of C 2-smooth Riemannian metrics g on a smooth manifold X, such that scalg(x) ≥ κ(x), is closed under C 0-limits of Riemannian metrics for all continuous functions κ on X. Apart from that our progress is limited but we formulate many conjectures. All along, we emphasize geometry,...
In this paper some relation among the Dirac operator on a Riemannian spin-manifold , its projection on some embedded hypersurface and the Dirac operator on with respect to the induced (called standard) spin structure are given.