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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 1861-1865 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The combination of Synge's approach to Einstein's equations with energy conditions and the Segré classification of the energy-momentum tensor is used in the examination of Einstein's space-time. An alternative physical interpretation for the Einstein static model is discussed. An Einstein-type moving fluid universe is presented. The meaning of both static space-time and static cosmological models are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 1127-1129 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The breakdown of causality in homogeneous Gödel-type space-time manifolds is examined. An extension of Rebouças–Tiomno (RT) and Accioly–Gonçalves studies is made. The existence of noncausal curves is also investigated under two different conditions on the energy-momentum tensor. An integral representation of the infinitesimal generators of isometries is obtained, extending previous works on the RT geometry.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 40 (1999), S. 4011-4027 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Five-dimensional (5D) generalized Gödel-type manifolds are examined in the light of the equivalence problem techniques, as formulated by Cartan. The necessary and sufficient conditions for local homogeneity of these 5D manifolds are derived. The local equivalence of these homogeneous Riemannian manifolds is studied. It is found that they are characterized by three essential parameters k, m2, and ω: identical triads (k,m2,ω) correspond to locally equivalent 5D manifolds. An irreducible set of isometrically nonequivalent 5D locally homogeneous Riemannian generalized Gödel-type metrics are exhibited. A classification of these manifolds based on the essential parameters is presented, and the Killing vector fields as well as the corresponding Lie algebra of each class are determined. It is shown that the generalized Gödel-type 5D manifolds admit maximal group of isometry Gr with r=7, r=9, or r=15 depending on the essential parameters k, m2, and ω. The breakdown of causality in all these classes of homogeneous Gödel-type manifolds are also examined. It is found that in three out of the six irreducible classes the causality can be violated. The unique generalized Gödel-type solution of the induced matter (IM) field equations is found. The question as to whether the induced matter version of general relativity is an effective therapy for these types of causal anomalies of general relativity is also discussed in connection with a recent work by Romero, Tavakol, and Zalaletdinov. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 39 (1998), S. 2180-2192 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The five-dimensional (5D) Riemannian Gödel-type manifolds are examined in light of the equivalence problem techniques, as formulated by Cartan. The necessary and sufficient conditions for local homogeneity of these 5D manifolds are derived. The local equivalence of these homogeneous Riemannian manifolds is studied. It is found that they are characterized by two essential parameters m2 and ω: identical pairs (m2,ω) correspond to locally equivalent 5D manifolds. An irreducible set of isometrically nonequivalent 5D locally homogeneous Riemannian Gödel-type metrics are exhibited. A classification of these manifolds based on the essential parameters is presented, and the Killing vector fields as well as the corresponding Lie algebra of each class are determined. It is shown that apart from the (m2=4ω2,ω≠0) and (m2≠0,ω=0) classes the homogeneous Riemannian Gödel-type manifolds admit a seven-parameter maximal group of isometry (G7). The special class (m2=4ω2,ω≠0) and the degenerated Gödel-type class (m2≠0,ω=0) are shown to have a G9 as maximal group of motion. The breakdown of causality in these classes of homogeneous Gödel-type manifolds are also examined. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 33 (1992), S. 2855-2862 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A new homogeneous space-time with seven isometries is derived by means of a complex transformation. It is shown that it is conformally flat and its Weyl-flat form is exhibited. Its Killing vector fields and the corresponding Lie algebra are also presented. An integral representation of these vector fields is found. Sources for the new space-time geometry are obtained by combining Synge's approach to Einstein's equations with energy conditions and Segrè classification of the energy-momentum tensors. A comparison with other rare space-times possessing a G7 of motions is made by using a suite of computer algebra programs.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 33 (1992), S. 2574-2577 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The basic problem of equivalence of gravitational fields in the framework of torsion theories of gravitation is solved. A coordinate-invariant description of the gravitational field is then presented. Explicit expressions for the dimensions of the group of transformations and its subgroup of isotropy are derived.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 36 (1995), S. 3074-3084 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: An algebraic classification of second order symmetric tensors in five-dimensional Kaluza–Klein-type Lorentzian spaces is presented by using Jordan matrices. It is shown that the possible Segre types are [1,1111], [2111], [311], [zz¯111], and the degeneracies thereof. A set of canonical forms for each Segre type is found. The possible continuous groups of symmetry for each canonical form are also studied. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 34 (1993), S. 186-192 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Canonical forms for the energy–momentum tensor of the scalar field in the framework of general relativity are derived and algebraically classified. Four different types arise depending on the vectorial character of the gradient of the scalar field. For each canonical form a solution of the Einstein-massless scalar field equations is presented. There emerges from our investigation alternative physical interpretation for two known space–times.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 27 (1986), S. 1370-1372 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The Gödel-type space-times are examined under different conditions on the algebraic structure of the energy-momentum tensor. A generalization of the Bampi–Zordan theorem on Gödel-type models is given. Chakraborty's results are recast as a special case of the generalized Bampi–Zordan theorem. The Rebouças–Tiomno solution is shown to be the unique Gödel-type metric with an algebraic structure of the tachyon fluid type.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation and analytical utility of several electrophone derivatives of native and oxidatively modified nucleosides of deoxythymidine and deoxyguanosine were studied. Derivatives include the incorporation of trimethylsilyl, acetyl or perfluoroacyl groups together with pentafluorobenzyl. Acetylation followed by pentafluorobenzylation was the most favourable method. In general, the combined information from the electron impact, positive ion chemical ionization and negative ion chemical ionization spectra was well suited for structure elucidation purposes. The acetyl-pentafluorobenzyl derivative of deoxythymidine was prepared in quantitative yield and was very sensitive on analysis by gas chromatography negative ion chemical ionization. Injection of 0.45 fmol of 3′,5′-bis(O-acetyl)-3-pentafluorobenzyl-deoxythymidine, in multiple ion detection experiments, gave a response with a signal-to-noise ratio larger than 10.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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