Yazar "Dil, Emre" seçeneğine göre listele

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    Can quantum black holes be (q, p)-fermions?
    (World Scientific Publ Co Pte Ltd, 2017) Dil, Emre
    In this study, to investigate the very nature of quantum black holes, we try to relate three independent studies: (q, p)-deformed Fermi gas model, Verlinde's entropic gravity proposal and Strominger's quantum black holes obeying the deformed statistics. After summarizing Strominger's extremal quantum black holes, we represent the thermostatistics of (q, p)-fermions to reach the deformed entropy of the (q, p)-deformed Fermi gas model. Since Strominger's proposal claims that the quantum black holes obey deformed statistics, this motivates us to describe the statistics of quantum black holes with the (q, p)-deformed fermions. We then apply the Verlinde's entropic gravity proposal to the entropy of the (q, p)-deformed Fermi gas model which gives the two-parameter deformed Einstein equations describing the gravitational field equations of the extremal quantum black holes obeying the deformed statistics. We finally relate the obtained results with the recent study on other modification of Einstein equations obtained from entropic quantum corrections in the literature.
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    Cosmology of q-deformed dark matter and dark energy
    (Elsevier, 2017) Dil, Emre
    In this study, we propose a novel dark cosmology consisting an interacting q-deformed spinor field dark matter and scalar field dark energy. We investigate the proposed deformed dark cosmology in metric-affine Einstein- Cartan-Sciama-Kibble theory. Firstly, we construct the action integral of the model, in order to obtain the energy-momentum tensor of the deformed dark matter and dark energy, from which the energy density and pressure of the deformed dark matter and dark energy can be obtained, respectively. After obtaining the deformed energy densities and pressures, we set up the Friedmann equations, continuity equations and equation of motions for this dark model. Then, we obtain the attractor solutions and stability analysis of the model for the accelerated expansion phase of the universe. We also investigate the effect of deformation parameter on the stable accelerated expansion behavior. Consequently, by mapping the interaction term and the field potentials we present the relationship between them and obtain the constraint on the interaction term in order to obtain a stable attractor solution. (C) 2017 Elsevier B.V. All rights reserved.
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    Coupling q-Deformed Dark Energy to Dark Matter
    (Hindawi Ltd, 2016) Dil, Emre
    We propose a novel coupled dark energy model which is assumed to occur as a q-deformed scalar field and investigate whether it will provide an expanding universe phase. We consider the q-deformed dark energy as coupled to dark matter inhomogeneities. We performthe phase-space analysis of themodel by numericalmethods and find the late-time accelerated attractor solutions. The attractor solutions imply that the coupled q-deformed dark energy model is consistent with the conventional dark energy models satisfying an acceleration phase of universe. At the end, we compare the cosmological parameters of deformed and standard dark energy models and interpret the implications.
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    Deformed Statistics and Micro Black Holes
    (2017) Dil, Emre
    In this study, we focus on the micro black holes which are formed due to the Hawking radiation of a charged macro black hole. Wewill analyze the physical behavior of the micro black holes by obtaining the deformed Einstein equations with the aid of statisticalapproaches of Verlinde and Strominger. Since Strominger proposed that the underlying statistics obeyed by the micro black holes isdeformed statistics, we will consider the micro black holes as (q,p)-deformed fermions and obtain the deformed Einstein equationsby following the Verlinde’s entropic gravity approach. After obtaining the deformed Einstein equations, we will analyze the physicalbehavior of these black holes by representing and interpreting the solutions of these equations.
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    Dynamics of Mixed Dark Energy Domination in Teleparallel Gravity and Phase-Space Analysis
    (Hindawi Ltd, 2015) Dil, Emre; Kolay, Erdinc
    We consider a novel dark energy model to investigate whether it will provide an expanding universe phase. Here we propose a mixed dark energy domination which is constituted by tachyon, quintessence, and phantom scalar fields nonminimally coupled to gravity, in the absence of background dark matter and baryonic matter, in the framework of teleparallel gravity. We perform the phase-space analysis of the model by numerical methods and find the late-time accelerated attractor solutions implying the acceleration phase of universe.
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    Generalized parallel transport and coordinate transformations in f(R) gravity
    (Korean Physical Soc, 2016) Dil, Emre
    In this paper, we study the generalized parallel transport of vectors and generalized coordinate transformations between generalized reference frames described in f(R) gravity. After constructing the generalized parallel transport relations and the generalized transformation laws in f(R) gravity, we discuss the implications of these laws and present the differences between f(R) gravity and Einstein's general relativity. For a constant Ricci scalar case with de Sitter-like behavior for a de Sitter space-time, we find that the parallel transport is invariant under the conformal transformation from general relativity to f(R) gravity. However, for a non-de Sitter space-time, parallel transport differs by an extra field term.
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    Gravitational entropy of a Schwarzschild-type black hole
    (Korean Physical Soc, 2016) Dil, Emre
    In this study, Clifton, Ellis and Tavakol's gravitational entropy proposal is used to determine the entropy of free gravitational fields due to a spherical symmetric Schwarzschild-type black hole which is considered in the framework of f(R) gravity. In order to obtain the gravitational entropy, we calculate the Weyl tensor of the black hole to determine the Bel-Robinson tensor, giving the super energy density. By using the super energy density, we obtain the gravitational energy density and the gravitational temperature to calculate the gravitational entropy of the f(R) gravity black hole. This proposal can reproduce the Bekenstein-Hawking value in general relativity limit, but cannot reproduce it in the f(R) gravity case.
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    Interacting Dark Matter and q-Deformed Dark Energy Nonminimally Coupled to Gravity
    (Hindawi Ltd, 2016) Dil, Emre
    In this paper, we propose a new approach to study the dark sector of the universe by considering the dark energy as an emerging q-deformed bosonic scalar field which is not only interacting with the dark matter, but also nonminimally coupled to gravity, in the framework of standard Einsteinian gravity. In order to analyze the dynamic of the system, we first give the quantum field theoretical description of the q-deformed scalar field dark energy and then construct the action and the dynamical structure of this interacting and nonminimally coupled dark sector. As a second issue, we perform the phase-space analysis of the model to check the reliability of our proposal by searching the stable attractor solutions implying the late-time accelerating expansion phase of the universe.
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    On the entropic nature of unified interactions
    (Iop Publishing Ltd, 2019) Dil, Emre; Yumak, Tugrul
    In this paper, we generalize Verlinde's entropic gravity proposal on the other fundamental interactions of nature. We begin by introducing the entropic origin of the Coulomb's electrostatic force, and then the magnetic force, by assuming the holographic principle holds when a charged particle approaches a screen enclosing the emerged part of the spacetime due to a source. We assume that the entropy of the screen changes when the charge approaches as in the Verlinde's approach. Thereafter, we obtain the entropic Maxwell equations in both classical and covariant form by means of the holographic principle hold for the source. Considering the gauge covariant structure of the fundamental forces, we implicitly generalize the entropic origin of the electromagnetic force into the strong and weak nuclear forces. The possibility of the entropic origin of the all fundamental forces of nature is assumed to make a meaningful contribution to the unification scheme of the fundamental forces.
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    Solution of Deformed Einstein Equations and Quantum Black Holes
    (Hindawi Ltd, 2016) Dil, Emre; Kolay, Erdinc
    Recently, one-and two-parameter deformed Einstein equations have been studied for extremal quantum black holes which have been proposed to obey deformed statistics by Strominger. In this study, we give a deeper insight into the deformed Einstein equations and consider the solutions of these equations for the extremal quantum black holes. We then represent the implications of the solutions, such that the deformation parameters lead the charged black holes to have a smaller mass than the usual Reissner-Nordstr om black holes. This reduction in mass of a usual black hole can be considered as a transition from classical to quantum black hole regime.
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    Space Creation Mechanism during the Expansion of Universe
    (Hindawi Ltd, 2016) Dil, Emre
    We propose a novel mechanism related to the expansion of universe. Recently Verlinde's proposal has been applied to the deformed bosons being a candidate for the dark energy constituents, since the negative pressure of the deformed bosons. The expansion of universe is dependent on the dark energy and implies a creation of space; we admit that the space creation mechanism is related to the deformed bosons and so is the dark energy. In order to relate the dark energy and the mechanism for creation of space, we consider Verlinde's proposal including the Holographic principle for emergence of space, which was recently applied to the deformed bosons. To check the validity of our mechanism, we calculate the ratio of the size of universe before and after the expansion and compare the results with the observational data. We find that the results are consistent with each other and infer that the proposed mechanism works correctly.
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    Spinor Quintom Cosmology with Intrinsic Spin
    (Hindawi Ltd, 2016) Dil, Emre
    We consider a spinor quintom dark energy model with intrinsic spin, in the framework of Einstein-Cartan-Sciama-Kibble theory. After constructing the mathematical formalism of the model, we obtain the spin contributed total energy-momentum tensor giving the energy density and the pressure of the quintom model, and then we find the equation of state parameter, Hubble parameter, deceleration parameter, state finder parameter, and some distance parameter in terms of the spinor potential. Choosing suitable potentials leads to the quintom scenario crossing between quintessence and phantom epochs, or vice versa. Analyzing three quintom scenarios provides stable expansion phases avoiding Big Rip singularities and yielding matter dominated era through the stabilization of the spinor pressure via spin contribution. The stabilization in spinor pressure leads to neglecting it as compared to the increasing energy density and constituting a matter dominated stable expansion epoch.
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    String solutions in spherically-symmetric f(R) gravity vacuum
    (World Scientific Publ Co Pte Ltd, 2018) Dil, Emre
    Dynamical evolution of the cosmic string in a spherically symmetric f(R) gravity vacuum is studied for a closed and straight string. We first set the background spacetime metric for a constant curvature scalar R = R-0, and obtain the Killing fields for it. Using the standard gauge coordinates and constraints for both closed and straight strings, we present the equation of motions and find the solutions of them. We then analyze the dynamics of the string by studying the behavior of the string radius and periastron radius, with respect to both proper time and azimuthal angle, for various values of f(R) functions. Consequently, we conclude that the value of f(R) dramatically affects the closed string collapse time and the straight string angular deviation.
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    The varying cosmological constant: a new approximation to the Friedmann equations and universe model
    (Oxford Univ Press, 2018) Oztas, Ahmet M.; Dil, Emre; Smith, Michael L.
    We investigate the time-dependent nature of the cosmological constant, Lambda, of the Einstein Field Equation (EFE). Beginning with the Einstein-Hilbert action as our fundamental principle we develop a modified version of the EFE allowing the value of Lambda to vary as a function of time, Lambda (t), indirectly, for an expanding universe. We follow the evolving Lambda presuming four-dimensional space-time and a flat universe geometry and present derivations of Lambda (t) as functions of the Hubble constant, matter density, and volume changes which can be traced back to the radiation epoch. The models are more detailed descriptions of the Lambda dependence on cosmological factors than previous, allowing calculations of the important parameters, Omega(m) and Omega(r), to deep lookback times. Since we derive these without the need for extra dimensions or other special conditions our derivations are useful for model evaluation with astronomical data. This should aid resolution of several difficult problems of astronomy such as the best value for the Hubble constant at present and at recombination.
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    Time-varying q-deformed dark energy interacts with dark matter
    (World Scientific Publ Co Pte Ltd, 2018) Dil, Emre; Kolay, Erdinc
    We propose a new model for studying the dark constituents of the universe by regarding the dark energy as a q-deformed scalar field interacting with the dark matter, in the framework of standard general relativity. Here we assume that the number of particles in each mode of the q-deformed scalar field varies in time by the particle creation and annihilation. We first describe the q-deformed scalar field dark energy quantum-field theoretically, then construct the action and the dynamical structure of these interacting dark sectors, in order to study the dynamics of the model. We perform the phase space analysis of the model to confirm and interpret our proposal by searching the stable attractor solutions implying the late-time accelerating phase of the universe. We then obtain the result that when interaction and equation-of-state parameter of the dark matter evolve from the present day values into a particular value, the dark energy turns out to be a q-deformed scalar field.