Yazar "Tarhan, I" seçeneğine göre listele

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    Conformal collineations in string cosmology
    (World Scientific Publ Co Pte Ltd, 2002) Baysal, H; Camci, U; Tarhan, I; Yilmaz, I; Yavuz, I
    In this paper, we study the consequences of the existence of conformal collineations (CC) for string cloud in the context of general relativity. Especially, we interest in special conformal collineation (SCC), generated by a special affine conformal collineation (SACC) in the string cloud. Some results on the restrictions imposed by a conformal collineation symmetry in the string cloud are obtained.
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    Curvature inheritance symmetry in Riemannian spaces with applications to string cloud and string fluids
    (World Scientific Publ Co Pte Ltd, 1999) Yilmaz, I; Tarhan, I; Yavuz, I; Baysal, H; Camci, U
    We study, in this paper, curvature inheritance symmetry (CI), pound xi R-bcd(a) = 2 alpha R-bcd(a), where a is a scalar function, for string cloud and string fluid in the context of general relativity. Also, we have obtained some result when a proper CI (i.e., alpha not equal 0) is also a conformal Killing vector.
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    Generation of Bianchi type V universes filled with a perfect fluid
    (Springer, 2001) Camci, U; Yavuz, I; Baysal, H; Tarhan, I; Yilmaz, I
    Assuming a perfect fluid distribution of matter Bianchi type V space-time is considered and using a new generation technique it is shown that the field equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are obtained, and the geometrical and physical properties of these solutions discussed.
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    Ricci collineations of the Bianchi types I and III, and Kantowski-Sachs spacetimes
    (World Scientific Publ Co Pte Ltd, 2001) Camci, U; Baysal, H; Tarhan, I; Yilmaz, I; Yavuz, I
    Ricci collineations of the Bianchi types I and III, and Kantowski-Sachs spacetimes are classified according to their Ricci collineation vector (RCV) field of the form (I)-(iv) one component of xi (a)(x(b)) is nonzero, (v)-(x) two components of xi (a)(x(b)) are nonzero, and (xi)-(xiv) three components of xi (a)(x(b)) are nonzero. Their relation with isometries of the spacetimes is established. In case (v), when det(R-ab) = 0, some metrics are found under the time transformation, in which some of these metrics are known, and the other ones new. Finally, the family of contracted Ricci collineations (CRC) are presented.
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    Rotating string cosmologies with scalar field and heat flux
    (World Scientific Publ Co Pte Ltd, 2001) Baysal, H; Yilmaz, I; Tarhan, I
    We obtain some cosmological model that axe exact solutions of Einstein field equations. The metric utilized is the nonstatic Godel-type cosmological model and the curvature source is a string cloud with scalar field and heat flow. The solutions have nonzero expansion, shear, and rotating. The properties of the solutions are studied and the temperature distribution is also given explicitly.
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    Some cosmological models with perfect fluid, scalar field and heat flux in rotating universe
    (Wiley-V C H Verlag Gmbh, 2002) Tarhan, I
    The dynamics of a radiating perfect fluid universe coupled with scalar field and heat flux are studied in the nonstatic Godel-type universe including the cosmological constant and obtained some exact solutions of Einstein field equations. The solutions have nonzero expansion, shear, and rotating universe. Various physical and geometrical properties of the model are also discussed and the temperature distribution is also given explicitly.
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    Some string cosmological models in Bianchi Type I space-time
    (Kluwer Academic Publ, 1996) Yavuz, I; Tarhan, I
    We obtain some cosmological models that are exact solutions of Einstein's field equations. The metric utilized is Marder's metric which is Bianchi Type I and the curvature source is a cloud of strings which are one dimensional objects. Bianchi type cosmological models play an important role in the study of the universe on a scale which anisotropy is not ignored. In this paper we have investigated the effect of cosmic strings on the cosmic microwave background anisotropy. Various physical and geometrical properties of the model are also discussed. The solutions have reported that the cosmic microwave background anisotropy may due to the cosmic strings.