Korunur, Murat; Korunur, Sibel

In this study, the energy density for the Levi-Civita space-time is analyzed within the framework of Rainbow Gravity Theory (RGT). RGT is a theoretical approach that assumes the geometry of space-time depends on the energy of the test particle, offering a promising perspective in the quest for quantum gravity. Energy densities are calculated using the Einstein, Bergmann-Thomson, and Landau-Lifshitz energy-momentum prescriptions and compared with the results obtained from General Relativity. The findings reveal that as the test particle’s energy increases, the energy density rises in the Einstein and Landau-Lifshitz prescriptions, while it decreases in the Bergmann-Thomson formulation. This highlights how the problem of energy localization varies across different energy-momentum definitions and demonstrates the impact of RGT on energy distribution. The study contributes to the literature exploring the influence of alternative gravitational theories on energy-momentum distributions.

İncele

Korunur, Murat; Korunur, Sibel

In this study, we consider a cosmological model based on Rényi holographic dark energy within the context of an anisotropic Bianchi type III spacetime geometry. The dark energy density is taken as a modified function of the Hubble parameter, which enables us to express the Einstein field equations in a closed dynamical system. By solving these equations, we obtain the evolution of the Hubble parameter and examine the main cosmological implications of the model. The physical behavior of the universe is discussed through the analysis of the equation-of-state parameter as well as the deceleration parameter. Our results indicate that the universe evolves from an initial decelerated expansion phase toward a late-time accelerated regime. In the asymptotic limit, the model tends to a de Sitter phase, suggesting the presence of a stable attractor configuration. In addition, we reconstruct the dark energy component in terms of different scalar field frameworks, namely quintessence, tachyon, and k-essence models. The associated scalar fields and their potentials are derived and numerically investigated. The obtained results show a coherent late-time behavior, which is in agreement with the observed accelerated expansion of the universe. The small value of the mean anisotropy parameter indicates that this evolution occurs within a quasi-isotropic Bianchi type III background.

İncele

Korunur, Murat; Korunur, Sibel

It is known that the general theory of relativity provides valuable answers about our universe. General relativity theory is used to describe space, time, and mass-energy interactions, while quantum theory is used to explain the behavior and interactions of microscopic particles. The gap between these two theories reveals the need to develop a unified theory of "quantum gravity". However, so far no universal theory has yet been found that fully resolves this conflict. This is a big puzzle that physicists have been working on for a long time, and unifying these two theories harmoniously is one of the biggest challenges in modern physics. One of the theories put forward for this purpose is the "Rainbow" theory of gravity. In this study, Einstein, Bergmann-Thomson and Landau-Lifshitz energy densities are calculated for a spatial self-similar, locally rotationally symmetric model using teleparallel geometry within the framework of the Rainbow theory of gravity. However, the results obtained are evaluated using rainbow functions that are well known in the literature. The obtained results are rewritten as explicit forms of energy densities for Einstein, Bergman-Thomson and Landau-Liftshitz representations using f_1 (\\chi)=1/(1-\\chi)and f_2 (\\chi)=1 rainbow functions. Accordingly, it has been shown that the test particle changes its energy density for the Einstein and Bergmann-Thomson energy-momentum prescriptions but does not change the energy density for the Landau-Liftshitz energy-momentum prescription.

İncele

Korunur, Murat; Korunur, Sibel

In this study, the energy-momentum localization problem is addressed within the framework of rainbow gravity. Considering the black string black hole, one of the cylindrical black hole models, energy-momentum distributions are obtained for Einstein, Bergmann-Thomson, and Landau-Liftshitz prescriptions in rainbow gravity. All prescriptions' energy densities are non-zero and depend on the rainbow functions, while the momentum distributions are zero. It has been observed that space-time energy does not depend on the energy of the test particle for some particular choices of rainbow functions. The results obtained for all special cases are given in a table.

AtıfScopus4·WoS4·OpenAlex4

İncele

Korunur, Murat; Korunur, Sibel

A wide variety of cosmological observations show us that our universe is in an accelerated expansion phase. Dark Energy and Dark Matter are thought to be two of the causes of this accelerated expansion. Therefore, scientists have recently been doing many studies on dark energy and matter. In particular, many energy density relations are written, and research is done about space-time structure. In this sense, the Tsallis holographic dark energy model is also in a current and interesting position. The study establishes a relationship between the Tsallis holographic dark energy (THDE) model and some scalar fields (quintessence, tachyon, dilaton scalar fields, etc.) specific to the Bianchi-type V space-time model. The relationship above is discussed within the Granda-Oliveros (GO) cut-off framework. The state equation parameter is calculated analytically, and the phase of our universe for this model is investigated with the graphs drawn. In addition, there is how the kinetic energy and the scalar potential change with time. The results are again analyzed numerically with graphs.

İncele

Korunur, Murat; Korunur, Sibel

Theoretical physicists generally prefer to modify the general theory of relativity rather than avoiding the successful approaches that have been offered to us. Hence, the rainbow formalism of gravity, which is one of the most studied quantum gravity candidates in literature, has recently gained importance in the field. In this study, the energy-momentum localization problem is discussed for the Taub universe within the framework of rainbow gravity. To achieve this goal, energy and momentum components are calculated by making use of diverse values of rainbow functions in the Einstein, Bergmann-Thomson, Landau-Lifshitz, and the Papapetrou prescriptions for the geometry under consideration. Except for the Landau-Lifshitz prescription, all prescriptions depend on the rainbow functions and the momentum components vanish. Graphical analysis is performed for all the energies obtained. Also, it is shown in limiting condition f1(x) → 1; f2(x) → 1 that the results are compatible with the ones obtained in the general relativity.

AtıfOpenAlex1

İncele

Korunur, Murat

Reconstruction process of scalar field models (quintessence, tachyon, dilaton and K-essence), which can be performed by making use of some dark energy density definitions such as holographic, Ricci, new agegraphic and ghost types proposals, has been an interesting and very attractive area to many physicists in literature. In this work, in a five-dimensional framework, we establish a correspondence between the quintessence, tachyon and the dilaton type scalar field definitions and the generalized ghost dark energy model by considering the extended form of the Kaluza-Klein (EKK) gravity. Accordingly, we numerically study the associated equation of state parameters, as well as their kinetic energy and scalar potential terms.

AtıfScopus5·WoS5·OpenAlex6

İncele

Korunur, Murat

The energy-momentum localization problem, which was attemted by Einstein himself for thefirst time, has been continued to the present day. Recently, new prescription obtained bymodifying the torsion theory and these results shed light on the solution of the energymomentum localisation problem. Focusing this purpose, we consider a Locally RotationallySymmetric Bianchi Type-II model in the teleparallel framework and calculate the modifiedenergy and momentum density for the general case. We also obtain the energy andmomentum density for some special cases of the modified theory and compare our resultswith previous work in the literature.

AtıfOpenAlex1

İncele

Korunur, Murat

In this paper, we study one of the new dark energy models named Tsallis holographic dark energy (THDE) model considering the Bianchi type-III spacetime model. Considering deceleration parameter, transition from deceleration to acceleration phase happens at z = 0.256. The equation of state (EoS) parameter has been found using the Granda-Oliveros (GO) scale. It is found that for > 2 values, EoS parameter behaves like the quintessence era; for < 2, EoS parameter behaves like the phantom dark energy and approaches CDM model at late-time cosmic acceleration phase. Also, we reconstructed a correspondence between THDE model and some well-known scalar fields, such as tachyon, quintessence and K-essence. In addition, we evaluated equation of state parameter, kinetic energy and scalar potential versus time.

AtıfScopus28·WoS28·OpenAlex29

İncele

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.

AtıfScopus15·WoS16·OpenAlex17

İncele

Korunur, Murat

In recent years, many studies have been conducted to reconstruct the physical properties of scalar fields by establishing a connection between some energy densities and a scalar field of dark energies. In this paper, using the extended five-dimensional (5D) Kaluza- Klein model, we establish a correspondence among modified holographic dark energy and the tachyon, K-essence and dilaton scalar-field models. We also graphically illustrate the evolution of the equation-of-state parameter versus time.

AtıfScopus7·WoS7·OpenAlex7

İncele

Korunur, Murat

Bu çalışmada, mutlak paralellizm olarak bilinen alternatif bir bakış açısıyla ünlü kütleçekim problemlerinden birini inceliyoruz. Bainchi-Type IX uzay-zamanın Taub çözümü ve mutlak paralellizmde Hamilton yaklaşımı tekniği göz önüne alındığında, bu duruma karşılık gelen açısal momentum, toplam enerji ve momentum dağılımları elde edilmektedir. Temel sonuçlarımızın diğer bir yazar tarafından literatürde yayınlanan sonuçlarla uyumlu olduğu görülmektedir

İncele

Korunur, Murat

In this work, under the assumption that the universe is locally rotationally symmetric (LRS) Bianchi type-II and filled with anisotropic dark uid (dark energy and dark radiation), we investigate whether the generalized second law of thermodynamics (GSLT) is still valid. We also consider another important condition for LRS Bianchi type-II spacetimes whereby the model expansion is proportional to the shear, which leads to B = An (where n is a constant and A and B are the metric potentials). Based on this, we derive a general circumstance for the GSLT and find that its validity depends on the anisotropies of both the dark uid and the metric potentials. We conclude that the GSLT still holds at all times even if these two anisotropic conditions are removed from the results.

AtıfScopus3·WoS3·OpenAlex3

İncele