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Classification results on purely magnetic perfect fluid models
No full textThe classification scheme for the complete class of purely electric perfect fluids (PEpf's) of Petrov type D has been worked out and the main results are presented. The Bianchi identities imply a subdivision of the solutions into three classes, with some remarkable characteristic properties. Already known PEpf solutions of Petrov type D are categorized. The scheme encloses previous classification results by Carminati, Wainwright, Barnes, Rowlingson and Collins
Purely electric perfect fluids of Petrov type D
No full textA non-conformally flat perfect fluid model for which the electric part of the Weyl tensor w.r.t. the fluid 4-velocity field vanishes, is called a purely magnetic perfect fluid (PMpf). Recently we showed that algebraically special PMpf's are necessarily locally rotationally symmetric, and hence are all known. Secondly, the class of algebraically general, non-accelerating PMpf's was explored. The dust case is conjectured to be inconsistent because of a particular mathematical feature in the governing equations. The remaining irrotational subclass contains a physically plausible and essentially unique member
Complete classification of the Wainwright Petrov type D perfect fluid models
No full textPerfect fluid spacetimes of Petrov type D, for which the fluid's four-velocity, the vorticity vector and one of the shear eigenvectors lie in the plane of principal null directions at each point, were naturally subdivided by Wainwright into four classes. The complete classification of these models is presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Maximally inhomogeneous Gödel-Farnsworth-Kerr generalizations
No full textIt is pointed out that physically meaningful aligned Petrov type D perfect fluid space-times with constant zero-order Riemann invariants are either the homogeneous solutions found by Gödel (isotropic case) and Farnsworth and Kerr (anisotropic case), or new inhomogeneous generalizations of these with non-constant rotation. We present the construction of the line element and the local geometric properties for the latter
Applications of the ortho-complex-null (OCN) formalism to perfect fluids
No full textThe OCN formalism is a weighted formalism which singles out two mutually orthogonal vector fields on a 4D space-time, one unit timelike and one unit spacelike, thereby leaving a phase freedom to the complex null directions orthogonal to them. It is of great aid to deduce novel exact solution families wherein two such fields are naturally distinguished. I will first outline the formalism and then present a substantive list of new results which can be obtained by means of it, regarding Weyl-aligned Petrov type D prefect fluid models on the one hand and the integrability proof for a new class of Petrov type I gravito-electric rotating dust space-times on the other
Expanding perfect fluid generalizations of the C metric
No full textPetrov type D gravitational fields, generated by a perfect fluid with spatially homogeneous energy density and with flow lines which form a nonshearing and nonrotating timelike congruence, are reexamined. It turns out that the anisotropic such spacetimes, which comprise the vacuum C metric as a limit case, can have nonzero expansion, contrary to the conclusion in the original investigation by Barnes [A. Barnes, Gen. Relativ. Gravit. 4, 105 (1973).]. Apart from the static members, this class consists of cosmological models with precisely one symmetry. The general line element is constructed and some important properties are discussed. It is also shown that purely electric Petrov type D vacuum spacetimes admit shear-free normal timelike congruences everywhere, even in the nonstatic regions. This result incited to deduce intrinsic, easily testable criteria regarding shear-free normality and staticity of Petrov type D spacetimes in general, which are added in an appendix
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