750 research outputs found
K\"ahler metrics via Lorentzian Geometry in dimension four
Given a semi-Riemannian -manifold with two distinguished vector
fields satisfying properties determined by their shear, twist and various Lie
bracket relations, a family of K\"ahler metrics is constructed, defined
on an open set in , which coincides with in many typical examples. Under
certain conditions and share various properties, such as a Killing
vector field or a vector field with a geodesic flow. In some cases the K\"ahler
metrics are complete. The Ricci and scalar curvatures of are computed
under certain assumptions in terms of data associated to . Many examples are
described, including classical spacetimes in warped products, for instance de
Sitter spacetime, as well as gravitational plane waves, metrics of Petrov type
such as Kerr and NUT metrics, and metrics for which is an SKR metric.
For the latter an inverse ansatz is described, constructing from the SKR
metric.Comment: This version contains minor additions: Sec. 4.4, and further material
on completeness (sec. 9.5). A sequel arXiv:1811.08999 contains
K\"ahler-Einstein and other metrics obtained by the constructio
Credible Equilibria in Games with Utility Changing during the Play
Publicado por Tilburg Center Economic Research 1992Whenever one deals with an interactive decision situation of long duration, one has to take into account
that priorities of the participants may change during the conflicto In this paper we propose an extensiveform
game model to handle such situations and suggest and study a solution concept, called credible equilibrium, which generalizes the concept of Nash equilibrium. We also discuss possible variants to this concept and applications of the model to other types of games
- …