Yazar "Yilmaz, 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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    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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    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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    Rigidly rotating strange quark stars
    (World Scientific Publ Co Pte Ltd, 2005) Yilmaz, I; Baysal, H
    In this article, we study rotating strange quark stars in the context of general relativity. For this purpose we consider perfect fluid model composed of strange quark matter with electromagnetic field in the Godel Universe which has rigid rotation. We solve Einstein's field equations by using equation of state for strange quark matter. Also, we discuss the features of obtained solutions.
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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 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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    Spacelike Ricci inheritance vectors in a model of string cloud and string fluid stress tensor
    (Iop Publishing Ltd, 2002) Baysal, H; Yilmaz, I
    We study the consequences of the existence of spacelike Ricci inheritance vectors (SpRIVs) parallel to x(alpha) for a model of string cloud and string fluid stress tensor in the context of general relativity. Necessary and sufficient conditions are derived for a spacetime with a model of string cloud and string fluid stress tensor to admit a SpRIV, and a SpRIV which is also a spacelike conformal Killing vector. Also, some results are obtained.
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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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    Timelike and spacelike Ricci colloneation vectors in string cosmology
    (World Scientific Publ Co Pte Ltd, 2001) Yilmaz, I
    In this paper, we study the consequences of the existence of timelike and spacelike Ricci collineation vectors (RCVs) for string cloud in the context of general relativity. Necessary and sufficient conditions are derived for a space-time with string cloud to admit a timelike RCV parallel to u(a) and a spacelike RCV parallel to x(a). Also, some results are obtained.
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    Topological defect solutions in the spherically symmetric space-time admitting conformal motion
    (Springer/Plenum Publishers, 2005) Yilmaz, I; Aygün, M; Aygün, S
    In this paper, we have examined strings with monopole and electric field and domain walls with matter and electric field in the spherically symmetric space-time admitting a one-parameter group of conformal motions. For this purpose, we have solved Einstein's field equations for a spherically symmetric space-time via conformal motions. Also, we have discussed the features of the obtained solutions.