Yazar "Yavuz, I" seçeneğine göre listele

Listeleniyor 1 - 13 / 13
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    Classifications of Kantowski-Sachs, Bianchi types I and III spacetimes according to Ricci collineations
    (World Scientific Publ Co Pte Ltd, 2003) Camci, U; Yavuz, I
    The Ricci collineation classifications of Kantowski-Sachs, Bianchi types I and III space-times are studied according to their degenerate and non-degenerate Ricci tensor. When the Ricci tensor is degenerate, the special cases are classified and it is shown that there are many cases of Ricci collineations (RCs) with infinite number of degrees of freedom, and the group of RCs is ten-dimensional in some spacial cases. Furthermore, it is found that when the Ricci tensor is non-degenerate, the group of RCs is finite-dimensional, and we have only either four which coincides with the isometries or six proper RCs in addition to the four isometries.
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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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    Cylindrically-symmetric and inhomogeneous cosmological models with viscous fluid
    (Kluwer Academic Publ, 1997) Kilinc, CB; Yavuz, I
    In this paper, the Einstein field equations have been solved for cylindrically symmetric and inhomogeneous cosmological models with viscous fluid. Various physical and geometrical properties of the models are also discussed.
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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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    Inheriting conformal and special conformal killing vectors in string cosmology
    (Plenum Publ Corp, 1997) Yavuz, I; Yilmaz, I
    In this paper we study the consequences of the existence of conformal and special conformal Killing vectors (CKV, SCKV) for string cloud and string fluid in the context of general relativity. The inheritance symmetries of the string cloud and string fluid are discussed. Einstein's field equations have been solved for static spherically symmetric space-time with cloud and fluid of strings source via CKV.
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    Inhomogeneous cylindrically-symmetric models in string cosmology
    (Kluwer Academic Publ, 1996) Kilinc, CB; Yavuz, I
    In this paper, the Einstein field equations have been solved for inhomogeneous cylindrically symmetric space times with string source. Certain physical and geometrical properties of the models have been examined.
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    Ricci collineations of the Bianchi type II, VIII, and IX space-times
    (Plenum Publ Corp, 1996) Yavuz, I; Camci, U
    Ricci and contracted Ricci collineations of the Bianchi type II, VIII, and IX space-times, associated with the vector fields of the form (i) one component of xi(alpha)(x(b)) is different from zero and (ii) two components of xi(alpha)(x(b)) are different from zero, for a, b = 1, 2, 3, 4, are presented. In subcase (i.b), which is xi(alpha) = (0, xi(1)(x(alpha)), 0, 0), some known solutions are found, and in subcase (i.d), which is xi(alpha) = (0, 0, 0, xi(4)(x(alpha))) choosing S(t) = const. x R(t), the Bianchi type II, VIII, and IX spacetime is reduced to the Robertson-Walker metric.
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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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    Some exact solutions of string cosmology with heat flux in bianchi type III space-time
    (Kluwer Academic Publ, 1996) Yavuz, I; Yilmaz, I
    In this paper, the Einstein field equations have been solved for a cloud of string with heat flux in Bianchi type III space-time. The physical and geometrical properties of the model have been examined.
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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.
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    Strange quark matter attached to the string cloud. in the spherical symmetric space-time admitting conformal motion
    (World Scientific Publ Co Pte Ltd, 2005) Yavuz, I; Yilmaz, I; Baysal, H
    In this paper, we have examined charged strange quark matter attached to the string cloud in the spherical symmetric space-time admitting one-parameter group of conformal motions. For this purpose, we have solved, Einstein's field equations for spherical symmetric space-time with strange quark matter attached to the string cloud via conformal motions. Also, we have discussed the features of the obtained solutions.
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    String cosmology with magnetic field in cylindrically symmetric space-time
    (Kluwer Academic Publ, 2000) Kilinç, CB; Yavuz, I
    In this paper, the Einstein field equations have been solved for inhomogeneous cylindrically symmetric space with string source in the presence of magnetic field. Certain physical and geometrical properties of the models have been examined. Also, the string solutions in which magnetic field are absent are discussed.