In this paper, conformal symmetric Freidmann–Robertson–Walker (FRW) universe with perfect fluid in the framework of [Formula: see text] gravitational theory is investigated. Firstly, field equations of FRW universe with perfect fluid are obtained for [Formula: see text] modified theory of gravity. The field equations of the model have been revised to understand physical nature between matter and geometry by means of conformal symmetry in [Formula: see text] gravitational theory. The exact solutions of conformal FRW universe with perfect fluid are attained for matter part of the [Formula: see text] model in the case of [Formula: see text]. The [Formula: see text] gravitational theory is one of the acceptable modifications of General Relativity (GR) in order to expound cosmic acceleration of the universe with no needing any exotic component. Nevertheless, the obtained model indicates exotic matter distribution for the current selection of arbitrary constants. Also, different value selections of arbitrary constants for the obtained model are able to predicate expanding or contracting universe with zero deceleration. Besides, it is shown that the FRW universe under the influence of the conformal Killing vector preserves to isotropic nature. Energy conditions are investigated. Also, it is shown that the constructed model satisfies strong energy condition (SEC) in all cases.

In this study, we investigate the Bianchi type-I cosmologies with string cloud attached to perfect fluid in f(R) gravity. The field equations and their exact solutions for Bianchi type-I cosmologies with string cloud attached to a perfect fluid are found by using the conformal symmetry properties. The obtained solutions under the varied selection of arbitrary constants indicate three cosmological models. Isotropy conditions for obtained cosmological models are investigated for large value of time. Whether or not the string cloud in conformal symmetric Bianchi type-I universe supports the isotropy condition for the large value of time has been investigated. Also, we examine the contracting and decelerating features of the obtained solutions by using Raychaudhuri equation. Finally, geometrical and physical results of the solutions are discussed.

In this study, it has been investigated whether the energy and momentum can be localizable for five-dimensional homogeneous and anisotropic universes. In this connection, energy and momentum of five-dimensional Bianchi type-I, type-III and type-V spacetimes have been calculated in the framework of general relativity (GR) and teleparallel gravity (TG). Einstein, Bergmann-Thomson, Landau-Lifshitz, Papapetrou, Tolman and Møller energy-momentum complexes have been used to obtain 1250078-1 Int. J. Mod. Phys. D 2012.21. Downloaded from www.worldscientific.com by UNIVERSITY OF MICHIGAN on 11/01/14. For personal use only. M. U. Dogru et al.these related quantities of given the spacetimes in GR, while Einstein, BergmannThomson, Landau-Lifshitz and Møller prescriptions have been used to obtain these related quantities of the spacetimes in TG. It has been found that all of the energy and momentum distributions of five-dimensional Bianchi type-I spacetime are equal to zero in GR and TG. For five-dimensional Bianchi type-III and type-V spacetimes, Bergmann-Thomson, Einstein and Tolman energy and momentum components give the same results, however Møller, Landau-Lifshitz and Papapetrou energy-momentum distributions give different results in general relativity. Also, in TG, Bergmann-Thomson and Einstein energy and momentum components give the same results for the Bianchi type-III and type-V spacetimes, too. In this sense, it is seen that Einstein, BergmannThomson and Landau-Lifshitz energy and momentum descriptions of these spacetimes have been given same results in both theories, GR and TG.

In this paper, we devote to investigate the energy-momentum problem of higher dimensional black holes in the general theory of relativity. The energy and momentum complex of Møller has been used for the calculations. Also, total energy and total momentum of some special cases for higher dimensional black holes such as Schwarzschild-like black holes, Reissner-Nordström-like charged black holes, AdS-like black holes, topological black holes, BTZ-like and charged BTZ-like black holes were obtained. It is invented that the momentum of black holes vanishes everywhere while the energy of black holes are not equal to zero in higher dimension. Also the results agree with Yang and Radinschi or Vagenas results M. Ulu Dogru ( ) · N.

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