2,216 research outputs found
Killing spinor space-times and constant-eigenvalue Killing tensors
A class of Petrov type D Killing spinor space-times is presented, having the
peculiar property that their conformal representants can only admit Killing
tensors with constant eigenvalues.Comment: 11 pages, submitted to CQ
Rotating solenoidal perfect fluids of Petrov type D
We prove that aligned Petrov type D perfect fluids for which the vorticity
vector is not orthogonal to the plane of repeated principal null directions and
for which the magnetic part of the Weyl tensor with respect to the fluid
velocity has vanishing divergence, are necessarily purely electric or locally
rotationally symmetric. The LRS metrics are presented explicitly.Comment: 6 pages, no figure
Petrov type D pure radiation fields of Kundt's class
We present all Petrov type D pure radiation space-times, with or without
cosmological constant, with a shear-free, non-diverging geodesic principal null
congruence
The deformation complex is a homotopy invariant of a homotopy algebra
To a homotopy algebra one may associate its deformation complex, which is
naturally a differential graded Lie algebra. We show that infinity
quasi-isomorphic homotopy algebras have L-infinity quasi-isomorphic deformation
complexes by an explicit construction.Comment: A revised version. The final version will appear in the volume
"Current Developments and Retrospectives in Lie Theory
Algebraically general, gravito-electric rotating dust
The class of gravito-electric, algebraically general, rotating `silent' dust
space-times is studied. The main invariant properties are deduced. The number
of functionally independent zero-order Riemann invariants satisfies
and special attention is given to the subclass .
Whereas there are no -term limits comprised in the class, the limit
for vanishing vorticity leads to two previously derived irrotational dust
families with , and the shear-free limit is the G\"{o}del universe.Comment: 10 pages, changed to revtex style, extended discussion section, minor
correction
Shear-free perfect fluids with a solenoidal electric curvature
We prove that the vorticity or the expansion vanishes for any shear-free
perfect fluid solution of the Einstein field equations where the pressure
satisfies a barotropic equation of state and the spatial divergence of the
electric part of the Weyl tensor is zero.Comment: 9 page
Purely radiative irrotational dust spacetimes
We consider irrotational dust spacetimes in the full non-linear regime which
are "purely radiative" in the sense that the gravitational field satisfies the
covariant transverse conditions div(H) = div(E) = 0. Within this family we show
that the Bianchi class A spatially homogeneous dust models are uniquely
characterised by the condition that is diagonal in the shear-eigenframe.Comment: 6 pages, ERE 2006 conference, minor correction
Purely radiative perfect fluids
We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids
with non-constant pressure and show that the Bianchi class A perfect fluids can
be uniquely characterized --modulo the class of purely electric and
(pseudo-)spherically symmetric universes-- as those models for which the
magnetic and electric part of the Weyl tensor and the shear are simultaneously
diagonalizable. For the case of constant pressure the same conclusion holds
provided one also assumes that the fluid is irrotational.Comment: 12 pages, minor grammatical change
Shearfree perfect fluids with solenoidal magnetic curvature and a gamma-law equation of state
We show that shearfree perfect fluids obeying an equation of state p=(gamma
-1) mu are non-rotating or non-expanding under the assumption that the spatial
divergence of the magnetic part of the Weyl tensor is zero.Comment: 11 page
Voedselecologie en gedrag van overwinterende watervogels langs de Zeeschelde: een methodologische studie
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