Yazar "Turkoglu, Murat Metehan" seçeneğine göre listele

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    Öğe
    Conformal cylindrically symmetric spacetimes in modified gravity
    (World Scientific Publ Co Pte Ltd, 2015) Turkoglu, Murat Metehan; Dogru, Melis Ulu
    We investigate cylindrically symmetric spacetimes in the context of f(R) gravity. We firstly attain conformal symmetry of the cylindrically symmetric spacetime. We obtain solutions to use features of the conformal symmetry, field equations and their solutions for cylindrically symmetric spacetime filled with various cosmic matters such as vacuum state, perfect fluid, anisotropic fluid, massive scalar field and their combinations. With the vacuum state solutions, we show that source of the spacetime curvature is considered as Casimir effect. Casimir force for given spacetime is found using Wald's axiomatic analysis. We expose that the Casimir force for Boulware, Hartle-Hawking and Unruh vacuum states could have attractive, repulsive and ineffective features. In the perfect fluid state, we show that matter form of the perfect fluid in given spacetime must only be dark energy. Also, we offer that potential of massive and massless scalar field are developed as an exact solution from the modified field equations. All solutions of field equations for vacuum case, perfect fluid and scalar field give a special f(R) function convenient to Lambda-CDM model. In addition to these solutions, we introduce conformal cylindrical symmetric solutions in the cases of different f(R) models. Finally, geometrical and physical results of the solutions are discussed.
  • [ X ]
    Öğe
    ENERGY CONTENTS OF THE WORMHOLES
    (World Scientific Publ Co Pte Ltd, 2011) Ulu, Melis; Turkoglu, Murat Metehan
    In this study, energy distributions of the various wormholes which connect two different parts of the universe have been investigated. We have obtained the energies of several types of wormholes as the statical wormholes, wormholes with scalar fields, electrical charged,Norm holes, zero density wormholes, zero radial tides wormholes, conformal wormholes, inflating wormholes, wormhole model in the Friedmann-Robertson-Walker (FEW) cosmology and Visser-Kar-Dadlich (VKD) wormholes using the Einstein, Weinberg and Landau-Lifshitz energy-momentum prescriptions. The Weinberg and Landau-Lifshitz energies of the statical wormholes, wormholes with scalar fields, electrical charged wormholes, zero density wormholes, zero radial tides wormholes or VKD-wormholes give the same results. Also, Weinberg, Landau-Lifshitz and Einstein energies of the conformal wormholes, inflating wormholes or wormholes in the FRW-cosmology give the different results.