Yazar "Acikgoz, I." seçeneğine göre listele

Listeleniyor 1 - 8 / 8
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    Extended Ricci and holographic dark energy models in fractal cosmology
    (Springer Heidelberg, 2014) Salti, M.; Korunur, M.; Acikgoz, I.
    We consider the fractal Friedmann-Robertson-Walker universe filled with dark fluid. By making use of this assumption, we discuss two types of dark energy models: Generalized Ricci and generalized holographic dark energies. We calculate the equation-of-state parameters, investigate some special limits of the results and discuss the physical implications via graphs. Also, we reconstruct the potential and the dynamics of the quintessence and k-essence (kinetic-quintessence) according to the results obtained for the fractal dark energy.
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    Finding Dirac Spin Effect in NUT Spacetime
    (Iop Publishing Ltd, 2010) Korunur, M.; Salti, M.; Acikgoz, I.
    In the present study, we are interested in finding the spin precession of a Dirac particle in expanding and rotating NUT spacetime. A tetrad with two functions to be determined is applied to the field equation of the teleparallel theory of gravity via a coordinate transformation. The vector, the axial-vector and the tensor parts of the torsion tensor are obtained. We found that the vector parts are in the radial and phi-directions. The axial-vector torsion is along r-direction while its other components along theta and phi-directions vanish everywhere. The vector connected with Dirac spin has been evaluated as well.
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    Ghost DBI-essence in fractal geometry
    (Springer Heidelberg, 2016) Acikgoz, I.; Binbay, F.; Salti, M.; Aydogdu, O.
    Focusing on a fractal geometric ghost dark energy, we reconstruct the Dirac-Born-Infeld (DBI)-essence-type scalar field and find exact solutions of the potential and warped brane tension. We also discuss statefinders for the selected dark energy description to make it distinguishable among others.
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    MATTER COLLINEATIONS OF BKS-TYPE SPACETIMES
    (Editura Acad Romane, 2014) Salti, M.; Korunur, M.; Acikgoz, I.; Binbay, F.; Pirinccioglu, N.
    In the present work, we classified the BKS-type (we refer to Bianchi-Kantowski-Sachs type spacetimes collectively as the BKS-type spacetimes) spacetimes (Bianchi type-V, Bianchi type-VI (m), Bianchi type-VI:(m), Kantowski-Sachs) according to their matter collineations when the energy-momentum tensor is degenerate and also when it is non-degenerate. We find that the dimension of matter collineations is infinite and we have improper matter collineations for the degenerate case (there are seven possibilities make the energy-momentum tensor to be degenerate). Next, for the non-degenerate case of the energy-momentum tensor, we obtain proper matter collineations and find the dimension of the group is finite.
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    MIBc AND THE DIRAC SPIN EFFECT IN TORSION GRAVITY
    (Editura Acad Romane, 2014) Salti, M.; Acikgoz, I.
    The spin precession of a Dirac particle in monotonically increasingly boosted coordinates is calculated using torsion gravity (teleparallel theory of gravity). Also, we find the vector and the axial-vector parts of the torsion tensor.
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    Polytropic Gas and Gravitational Thermodynamics
    (Elsevier, 2014) Salti, M.; Acikgoz, I.; Abedi, H.
    We mainly assume that our universe is locally rotationally symmetric (LRS) Bianchitype II and is filled with a combination of a polytropic gas and baryonic matter. Also, we consider the polytropic gas scenario as the unification of dark matter and dark energy. By making use of these assumptions, we investigate the first and second laws of gravitational thermodynamics on the apparent horizon.
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    SPIN-1/2 PARTICLES IN TORSION GRAVITY WHEN A CONSTANT ELECTRIC FIELD IS PRESENT
    (Editura Acad Romane, 2013) Keskin, A. I.; Binbay, F.; Salti, M.; Acikgoz, I.
    In this work, we focus on the dynamics of Dirac particles in the presence of a constant electric field in a cosmological anisotropic universe. Instead of Einstein's theory of general relativity, we perform the calculations using the teleparallel theory of gravity which is also called as the torsion gravity. First, we found the exact solution of the teleparallel Dirac equation in an anisotropic Bianchi-I universe. Second, the harmonic oscillator behaviour of the solution and then the quantization of oscillation frequency had been discussed. Third, we investigated the spin precession of Dirac particles and dispute the axial-vector spin coupling term.
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    Unified solutions of extended Gauss-Bonnet gravity
    (Springer, 2016) Keskin, A. I.; Acikgoz, I.
    We study some scale factor power-law solutions of the field equations of the extended Gauss Bonnet gravity in the spatial FRW (Friedmann-Robertson-Walker) universe. We consider the lagrangian density given by F(R, G) = f (G) + R + alpha R-2 which exhibits a modification comparing with the modified Gauss Bonnet gravity. After constructing the Friedmann equations and finding the power-law solution we obtain the real valued of our model describing a mechanism that shows transitions among three stages of the universe (inflation, deceleration, acceleration) in an unified way. In particular, in this unified solution we obtained an inflation model without using any scalar field description when alpha > 0, and also we verified our early time inflationary scenario using observational parameters, i.e. n(s), r. Further, we research for the power-law solution of our model when the universe is in the phantom phase. Here, it is observed that the acceleration of the universe in phantom region is composed of two phases which congruent with the recent observations.