828 research outputs found
Gravitational waves in vacuum spacetimes with cosmological constant. I. Classification and geometrical properties of non-twisting type N solutions
All non-twisting Petrov-type N solutions of vacuum Einstein field equations
with cosmological constant Lambda are summarized. They are shown to belong
either to the non-expanding Kundt class or to the expanding Robinson-Trautman
class. Invariant subclasses of each class are defined and the corresponding
metrics are given explicitly in suitable canonical coordinates. Relations
between the subclasses and their geometrical properties are analyzed. In the
subsequent paper these solutions are interpreted as exact gravitational waves
propagating in de Sitter or anti-de Sitter spacetimes.Comment: 16 pages, no figures, LaTeX, To appear in J. Math. Phy
Astrophysics Without Black Holes, and Without Extragalactic Gamma-Ray Bursts
Contrary to common belief, it is argued that our Universe contains neither Black Holes, nor Extracalactic Gamma-Ray Bursts
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