120435397
Irrotational perfect fluids with a purely electric Weyl tensor
All perfect fluid spacetimes with a purely electric Weyl tensor are shown to have an alignment between the fluid 4-velocity and a canonical null tetrad determined by the Weyl tensor. If, in addition, it is assumed that the flow is irrotational, the eigenframes of the shear and Weyl tensors coincide. In all but two rather special cases, it is proved that the vectors of this eigenframe are hypersurface orthogonal and consequently that a coordinate system exists in which the metric, shear and Eab (the electric part of the Weyl tensor) are all diagonal. Geodesic Petrov type D spacetimes are shown to be either Bianchi type 1 or to belong to the class of solutions considered by Szekeres (1975) and Szafron (1977). The Allnutt solutions (1982) are shown to be the only purely electric type D fields in which the shear is non-degenerate and in which the acceleration vector lies in the plane spanned by the principal null vectors. The field equations are partially integrated in two classes where no solutions are yet known.
121708777
A class of homogeneous Einstein-Maxwell fields
The author considers solutions of the Einstein-Maxwell field equations satisfying the conditions Fij;k+lk=fFij+, Fij;k+nk=gFij+ where Fij+ is the self-dual Maxwell bivector and li and ni are the principal null vectors of Fij+. The fields are algebraically general and the most general solution is found in closed form when li and ni have non-zero twist. Several twist-free solutions are also obtained. Vacuum space-times admitting a test Maxwell field are also considered. In all cases the metric admits a three-parameter group of motions acting transitively on three-dimensional orbits. Fields satisfying the dual conditions with li and ni replaced by mi and mi are also investigated and similar results are obtained.
13652721
Irreducible Killing Tensors from Conformal Killing Vectors
Koutras has proposed some methods to construct reducible proper conformal Killing tensorsand Killing tensors (which are, in general, irreducible) when a pair of orthogonal conformalKilling vectors exist in a given space. We give the completely general result demonstratingthat this severe restriction of orthogonality is unnecessary. In addition we correct andextend some results concerning Killing tensors constructed from a single conformal Killingvector. We give as an example a Kimura metric and demonstrate how it is possible toconstructalargerclassofreducibleproperconformalKillingtensorsandKillingtensorsthanpermitted by the Koutras algorithms. In addition, from our new result that all conformalKilling tensors are reducible in conformally ﬂat spaces, we have a method of constructingall conformal Killing tensors and hence all the Killing tensors (which will in general beirreducible) of conformally ﬂat spaces using their conformal Killing vectors.
118781109
Killing tensors from conformal Killing vectors
Some years ago Koutras presented a method of constructing a conformal Killing tensor from a pair of orthogonal conformal Killing vectors. When the vector associated with the conformal Killing tensor is a gradient, a Killing tensor (in general irreducible) can then be constructed. In this paper it is shown that the severe restriction of orthogonality is unnecessary and thus it is possible that many more Killing tensors can be constructed in this way. We also extend, and in one case correct, some results on Killing tensors constructed from a single conformal Killing vector. Weir's result that, for flat space, there are 84 independent conformal Killing tensors, all of which are reducible, is extended to conformally flat spacetimes. In conformally flat spacetimes it is thus possible to construct all the conformal Killing tensors and in particular all the Killing tensors (which in general will not be reducible) from conformal Killing vectors.
118984350
Comment on"Conformally flat stationary axisymmetric metrics"
Garcia and Campuzano claim to have found a previously overlooked family of stationary and axisymmetric conformally flat spacetimes, contradicting an old theorem of Collinson. In both these papers it is tacitly assumed that the isometry group is orthogonally transitive. Under the same assumption, we point out here that Collinson's result still holds if one demands the existence of an axis of symmetry on which the axial Killing vector vanishes. On the other hand if the assumption of orthogonal transitivity is dropped, a wider class of metrics is allowed and it is possible to find explicit counterexamples to Collinson's result.
15230558
Killing tensors and conformal Killing tensors from conformal Killing vectors
Koutras has proposed some methods to construct reducible proper conformal Killing tensors and Killing tensors (which are, in general, irreducible) when a pair of orthogonal conformal Killing vectors exist in a given space. We give the completely general result demonstrating that this severe restriction of orthogonality is unnecessary. In addition, we correct and extend some results concerning Killing tensors constructed from a single conformal Killing vector. A number of examples demonstrate that it is possible to construct a much larger class of reducible proper conformal Killing tensors and Killing tensors than permitted by the Koutras algorithms. In particular, by showing that all conformal Killing tensors are reducible in conformally flat spaces, we have a method of constructing all conformal Killing tensors, and hence all the Killing tensors (which will in general be irreducible) of conformally flat spaces using their conformal Killing vectors.
118861611
Observation of inclusive. omega. production at large transverse momentum
We have observed the production of ..omega.. mesons at large transverse momentum produced in 200-GeV/c pBe interactions. The ratio of inclusive production of ..omega.. to ..pi../sup 0/ at transverse momenta above 2.2 GeV/c is 0.44 +- 0.08 near x=0. The upper limit for eta' to eta production is <1.4 in the same kinematic region.