Ilhami Yavuz

Strange quark matter attached to the string cloud in the spherical symmetric space-time admitting conformal motion

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 Einsteins 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.

RICCI COLLINEATIONS OF THE BIANCHI TYPES I AND III, AND KANTOWSKI–SACHS SPACETIMES

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 ξa(xb) is nonzero, (v)–(x) two components of ξa(xb) are nonzero, and (xi)–(xiv) three components of ξa(xb) are nonzero. Their relation with isometries of the spacetimes is established. In case (v), when det(Rab)=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.

Inhomogeneous cylindrically-symmetric models in string cosmology

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.

Generation of Bianchi Type V Universes Filled with A Perfect Fluid

Assuming a perfect fluid distribution of matter Bianchi type Vspace-time is considered and using a new generation techniqueit is shown that the field equations are solvable for anyarbitrary cosmic scale function. Solutions for particularforms of cosmic scale functions are obtained, and thegeometrical and physical properties of these solutions discussed.

Some exact solutions of string cosmology with heat flux in Bianchi type III space-time

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.

CLASSIFICATIONS OF KANTOWSKI–SACHS, BIANCHI TYPES I AND III SPACETIMES ACCORDING TO RICCI COLLINEATIONS

The Ricci collineation classifications of Kantowski–Sachs, Bianchi types I and III spacetimes 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.

Some string cosmological models in Bianchi Type I space-time

We obtain some cosmological models that are exact solutions of Einsteins field equations. The metric utilized is Marders 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.

CONFORMAL COLLINEATIONS IN STRING COSMOLOGY

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.

CURVATURE INHERITANCE SYMMETRY IN RIEMANNIAN SPACES WITH APPLICATIONS TO STRING CLOUD AND STRING FLUIDS

We study, in this paper, curvature inheritance symmetry (CI), , where α 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., α ≠ 0) is also a conformal Killing vector.

Cylindrically-Symmetric and Inhomogeneous Cosmological Models with Viscous Fluid

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.