-connections compatible with homogeneous metric on the cotangent bundle.
Determination of the structure of algebraic curvature tensors by means of Young symmetrizers.
Diffeomorphisms conformal on distributions
Let f:M → N be a local diffeomorphism between Riemannian manifolds. We define the eigenvalues of f to be the eigenvalues of the self-adjoint, positive definite operator df*df:TM → TM, where df* denotes the operator adjoint to df. We show that if f is conformal on a distribution D, then , where denotes the eigenspace corresponding to the coefficient of conformality λ of f. Moreover, if f has distinct eigenvalues, then there is locally a distribution D such that f is conformal on D if and only...
Differential forms, Weitzenböck formulae and foliations.
The Weitzenböck formulae express the Laplacian of a differential form on an oriented Riemannian manifold in local coordinates, using the covariant derivatives of the form and the coefficients of the curvature tensor. In the first part, we shall describe a certain "differential algebra formalism" which seems to be a more natural frame for those formulae than the usual calculations in local coordinates.In this formalism there appear some interesting differential operators which may also be used to...
Differential geometry of geodesic spheres.
Doubly warped products with harmonic Weyl conformal curvature tensor