Yazar "Korunur, Murat" seçeneğine göre listele

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    Brane-world black holes and energy-momentum vector
    (Springer, 2006) Salti, Mustafa; Aydogdu, Oktay; Korunur, Murat
    The Brane-World black hole models are investigated to evaluate their relative energy and momentum components. We consider Einstein and Moller's energy-momentum prescriptions in general relativity, and also perform the calculation of energy-momentum density in Moller's tetrad theory of gravity. For the Brane-World black holes we show that although Einstein and Moller complexes, in general relativity give different energy relations, they yield the same results for the momentum components. In addition, we also make the calculation of the energy-momentum distribution in teleparallel gravity, and calculate exactly the same energy as that obtained by using Moller's energy-momentum prescription in general relativity. This interesting result supports the viewpoint of Lessner that the Moller energy-momentum complex is a powerful concept for the energy and momentum. We also give five different examples of Brane-World black holes and find the energy distributions associated with them. The result calculated in teleparallel gravity is also independent of the teleparallel dimensionless coupling constant, which means that it is valid in any teleparallel model. This study also sustains the importance of the energy-momentum definitions in the evaluation of the energy distribution of a given space-time, and supports the hypothesis by Cooperstock that the energy is confined to the region of non-vanishing energy-momentum tensor of matter and all non-gravitational fields.
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    Einstein-Maxwell-Dilaton-Aksiyon kuramı ve mutlak paralelizm
    (2016) Korunur, Murat; Açıkgöz, İrfan
    Bu tezde, Einstein-Maxwell-Dilaton-Aksiyon (EMDA) kuramı için kartezyen ve küresel koordinatlarda seçilen bazı evren modellerinin enerjileri ve/veya enerji-momentum yoğunlukları çeşitli gösterimler kullanılarak hesaplanmıştır. Ayrıca bu evren modelleri için aksiyal vektör burulmaları da hesaplanmıştır. Birinci bölümde giriş yapılmıştır. Kaynak araştırması kısmında mutlak paralelizm için bazı evren modellerinden elde edilen enerji ve/veya enerji yoğunlukları tarihsel bir akış içerisinde irdelenmiştir. Materyal ve metot kısmında kartezyen ve küresel koordinatlarda enerji ve/veya enerji yoğunluklarının nasıl hesaplandığı literatür temel alınarak verilmiştir. Bulgular ve tartışma kısmında ilk olarak homojen olmayan Einstein-Maxwell-Dilaton Aksiyon kuramı için enerji ve momentum yoğunlukları kartezyen koordinatlarda; Einstein, Bergman-Thomson ve Landau-Liftshitz gösterimleri kullanılarak, hesaplanmıştır. Sonrasında ise küresel koordinatlarda Einstein-Maxwell-Dilaton-Aksiyon kuramında yüklü kara delik modelleri için enerji, Moller gösterimi kullanılarak bazı özel durumlar için hesaplanmıştır. Son olarak, sonuç ve öneriler kısmında, bulunan sonuçlar irdelenmiş, konunun güncelliği ve yeni yapılacak çalışmalara nasıl ışık tutacağı belirtilmiştir.
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    Energy associated with the Gibbons-Maeda dilaton spacetime
    (Springer/Plenum Publishers, 2006) Aydogdu, Oktay; Salti, Mustafa; Korunur, Murat; Acikgoz, Irfan
    In order to obtain energy and momentum (due to matter and fields including gravitation) distributions of the Gibbons-Maeda dilaton spacetime, we use the Moller energy-momentum prescription both in Einsteins theory of general relativity and teleparallel gravity. We find the same energy distribution for a given metric in both of these different gravitation theories. Under two limits, we also calculate energy associated with two other models such as the Garfinkle-Horowitz-Strominger dilaton spacetime and the Reissner-Nordstrom spacetime. The energy obtained is also independent of the teleparallel dimensionless coupling constant, which means that it is valid in any teleparallel model. Our result also sustains (a) the importance of the energy-momentum definitions in the evaluation of the energy distribution for a given spacetime and (b) the viewpoint of Lessner that the Moller energy-momentum complex is a powerful concept of energy and momentum (c) the hypothesis of Vagenas that there is a connection between the coefficients of the energy-momentum expression of Einstein and those of Moller.
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    f(T,R) theory of gravity
    (World Scientific Publ Co Pte Ltd, 2018) Salti, Mustafa; Korunur, Murat; Acikgoz, Irfan; Pirinccioglu, Nurettin; Binbay, Figen
    We mainly focus on the idea that the dynamics of the whole universe may be understood by making use of torsion T and curvature R at the same time. The f(T, R)-gravity can be considered as a fundamental gravitational theory describing the evolution of the universe. The model can produce the unification of the general relativity (GR), teleparallel gravity (TPG), f(R)-gravity and f(T)-gravity theories. For this purpose, the corresponding Lagrangian density is written in terms of an arbitrary function of the torsion and curvature scalars. Furthermore, we use the absence/existence puzzle of relativistic neutron stars and thermodynamical laws as constraining tools for the new proposal.
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    Godel-type spacetimes in f(R)-gravity
    (De Gruyter Poland Sp Z O O, 2013) Salti, Mustafa; Korunur, Murat; Acikgoz, Irfan
    We focus on one of the famous problems in theoretical physics today: the problem of energy-momentum localization. Although many authors have endeavoured to solve this problem, it has remained unsolved until now. In this work, we consider the generalized version of the Landau-Lifshitz definition in f(R)-Gravity to discuss the energy-momentum localization problem in Godel-type metrics. We also take into account five popular f(R) models to obtain specific results.
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    The Lukash plane-wave attractor and relative energy
    (World Scientific Publ Co Pte Ltd, 2007) Korunur, Murat; Salti, Mustafa; Aydogdu, Oktay
    We study energy distribution in the context of teleparallel theory of gravity, due to matter and fields including gravitation, of the universe based on the plane-wave Bianchi VII delta spacetimes described by the Lukash metric. For this calculation, we consider the teleparallel gravity analogs of the energy momentum formulations of Einstein, Bergmann-Thomson and Landau-Lifshitz. We find that Einstein and Bergmann-Thomson prescriptions agree with each other and give the same results for the energy distribution in a given spacetime, but the Landau-Lifshitz complex does not. Energy density turns out to be nonvanishing in all of these prescriptions. It is interesting to mention that the results can be reduced to the already available results for the Milne universe when we write omega = 1 and Xi(2) = 1 in the metric of the Lukash spacetime, and for this special case, we get the same relation among the energy momentum formulations of Einstein, Bergmann Thomson and Landau-Lifshitz as obtained for the Lukash spacetime. Furthermore, our results support the hypothesis by Cooperstock that the energy is confined to the region of nonvanishing energy momentum tensor of matter and all non-gravitational fields, and also sustain the importance of the energy momentum definitions in the evaluation of the energy distribution associated with a given spacetime.
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    A non-diagonal singularity-free model in torsion gravity
    (De Gruyter Poland Sp Zoo, 2012) Korunur, Murat
    In the context of torsion (teleparallel) gravity, we focus on discussing the spin effects of Dirac particles associated with the non-diagonal singularity-free model (Mars space-time). We see that the vector part depends on the radial r and z directions and the axial-vector will be along the radial direction, that is, it will be symmetric about radial direction. Furthermore, the t = 0 case of the Mars metric is considered, thence it is seen that the axial-vector vanishes.
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    On the relative energy associated with space-times of diagonal metrics
    (Indian Acad Sciences, 2007) Korunur, Murat; Salt, Mustafa; Havare, Ali
    In order to evaluate the energy distribution (due to matter and fields including gravitation) associated with a space-time model of generalized diagonal metric, we consider the Einstein, Bergmann-Thomson and Landau-Lifshitz energy and/or momentum definitions both in Einstein's theory of general relativity and the teleparallel gravity (the tetrad theory of gravitation). We find same energy distribution using Einstein and Bergmann-Thomson formulations, but we also find that the energy-momentum prescription of Landau-Lifshitz disagree in general with these definitions. We also give eight different well-known space-time models as examples, and considering these models and using our results, we calculate the energy distributions associated with them. Furthermore, we show that for the Bianchi Type-I models all the formulations give the same result. This result agrees with the previous Works of Cooperstock-Israelit, Rosen, Johri et al, Banerjee-Sen, Xulu, Vargas and Salti et al and supports the viewpoints of Albrow and Tryon.
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    Total Energy of Charged Black Holes in Einstein-Maxwell-Dilaton-Axion Theory
    (Hindawi Ltd, 2012) Korunur, Murat; Acikgoz, Irfan
    We focus on the energy content (including matter and fields) of the Moller energy-momentum complex in the framework of Einstein-Maxwell-Dilaton-Axion (EMDA) theory using teleparallel gravity. We perform the required calculations for some specific charged black hole models, and we find that total energy distributions associated with asymptotically flat black holes are proportional to the gravitational mass. On the other hand, we see that the energy of the asymptotically nonflat black holes diverge in a limiting case.