Which smooth compact 4-manifolds admit an Einstein metric with non-negative Einstein constant? A complete answer is provided in the special case of 4-manifolds that also happen to admit either a complex structure or a symplectic structure. A Riemannian manifold (M, g) is said to be Einstein if it has constant Ricci curvature, in the sense that the function v −→ r(v, v) on the unit tangent bundl...

Abstract We continue our study of the mixed Einstein–Hilbert action as a functional pseudo-Riemannian metric and linear connection. Its geometrical part is total scalar curvature on smooth manifold endowed with distribution or foliation. develop variational formulas for quantities extrinsic geometry metric-affine space use them to derive Euler–Lagrange equations (which in case space-time are an...

It is proved that any compact almost Kähler, Einstein 4-manifold whose fundamental form is a root of the Weyl tensor is necessarily Kähler.

Using Ernst's theory of complex potentials, a solution of the coupled Einstein-Maxwell equations in oblate spheroidal coordinates is obtained for a source possessing mass, electric charge, and angular momentum. The density of the electromagnetic energy is evaluated. Explicit expressions are derived for the components of the Ricci tensor Rmunu, and of the electromagnetic energy momentum tensor E...

The Kähler metric which has been constructed by present author in [1] is used in this paper to find an exact solution of Einstein equations with energy-momentum tensor of special type. That type of Tij admits in particular to use it as energy-momentum tensor of charged scalar field and in case of such system the field function is determined.

It is well known that 4–dimensional Kerr–NUT–AdS spacetime possesses the hidden symmetry associated with the Killing–Yano tensor. This tensor is ‘universal’ in the sense that there exist coordinates where it does not depend on any of the free parameters of the metric. Recently the general higher dimensional Kerr–NUT–AdS solutions of the Einstein equations were obtained. We demonstrate that all ...

We compute the number of linearly independent ways in which a tensor of Weyl type may act upon a given irreducible tensor-spinor bundle V over a Riemannian manifold. Together with the analogous but easier problem involving actions of tensors of Einstein type, this enumerates the possible curvature actions on V.