Showing papers by "Jerzy Lewandowski published in 1990"
TL;DR: In this article, it was shown that the vacuum Einstein equations imposed on a metric which admits shear-free null and geodesic congruence imply the realizability of an associated CR structure.
Abstract: It is shown that the vacuum Einstein equations imposed on a metric which admits shear-free null and geodesic congruence imply the realizability of an associated CR structure.
38 citations
TL;DR: In this paper, a natural framework based on the theory of Cauchy-Riemann structures (CR) is derived to study gravitational fields with twisting shear-free geodesic null congruences.
Abstract: A natural framework based on the theory of Cauchy-Riemann structures (CR) is derived to study gravitational fields with twisting shear-free geodesic null congruences. The authors write down Einstein vacuum and pure radiation equations for these fields using Cartan's invariants of CR geometry. The case when the fields admit more than a two-dimensional conformal group of symmetries is solved completely. Among pure radiation solutions of this kind new solutions are obtained.
35 citations
TL;DR: In this article, the authors considered 4-dimensional Lorentzian geometries admitting a shearfree optical geometry and proved that all of them are geodesic iff the Weyl tensor is of Petrov type N and the metric admits a twisting null conformal-Killing vector field.
5 citations
TL;DR: In this article, it was shown that a spacetime for which the matter content is pure (null) shear-free and twisting radiation, with or without a cosmological constant cannot admit a proper conformal Killing vector field.
Abstract: The author shows that a spacetime for which the matter content is pure (null) shear-free and twisting radiation, with or without a cosmological constant cannot admit a proper conformal Killing vector field
3 citations