Cosmological Models with Linearly Varying Deceleration Parameter
- Özgür Akarsu, T. Dereli
- Physics
- 4 February 2011
We propose a new law for the deceleration parameter that varies linearly with time and covers Berman’s law where it is constant. Our law not only allows one to generalize many exact solutions that…
LRS Bianchi type I models with anisotropic dark energy and constant deceleration parameter
- Özgür Akarsu, C. Kılınç
- Physics
- 30 July 2008
Locally rotationally symmetric Bianchi type I cosmological models are examined in the presence of dynamically anisotropic dark energy and perfect fluid. We assume that the dark energy (DE) is…
de Sitter expansion with anisotropic fluid in Bianchi type-I space-time
- Özgür Akarsu, C. Kılınç
- Physics, Geology
- 4 January 2010
Some features of the Bianchi type-I universes in the presence of a fluid that wields an anisotropic equation of state (EoS) parameter are discussed in the context of general relativity. The models…
Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant
- Özgür Akarsu, J. Barrow, Luis A. Escamilla, J. Vázquez
- PhysicsPhysical Review D
- 19 December 2019
We study the cosmological constant (Λ) in the standard Λ cold dark matter model by introducing the graduated dark energy (gDE) characterized by a minimal dynamical deviation from the null inertial…
Bianchi type III models with anisotropic dark energy
- Özgür Akarsu, C. Kılınç
- Physics
- 7 September 2009
The general form of the anisotropy parameter of the expansion for Bianchi type-III metric is obtained in the presence of a single diagonal imperfect fluid with a dynamically anisotropic equation of…
Probing kinematics and fate of the Universe with linearly time-varying deceleration parameter
- Özgür Akarsu, T. Dereli, Suresh Kumar, Lixin Xu
- Mathematics, Physics
- 22 May 2013
The parametrizations q = q0+q1z and q = q0+q1(1 − a/a0) (Chevallier-Polarski-Linder parametrization) of the deceleration parameter, which are linear in cosmic redshift z and scale factor a , have…
Screening $$\Lambda $$ in a new modified gravity model
- Özgür Akarsu, J. Barrow, Charles V. R. Board, N. Uzun, J. Vázquez
- PhysicsThe European Physical Journal C
- 27 March 2019
We study a new model of Energy-Momentum Squared Gravity (EMSG), called Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term $$f(T_{\mu \nu }T^{\mu \nu })=\alpha \ln (\lambda…
Constraints on a Bianchi type I spacetime extension of the standard ΛCDM model
- Özgür Akarsu, Suresh Kumar, Shivani Sharma, L. Tedesco
- PhysicsPhysical Review D
- 16 May 2019
We consider the simplest anisotropic generalization, as a correction, to the standard $\Lambda$CDM model, by replacing the spatially flat Robertson-Walker metric by the Bianchi type-I metric, which…
Anisotropic inflation with a non-minimally coupled electromagnetic field to gravity
- M. Adak, Özgür Akarsu, T. Dereli, Özcan Sert
- Geology
- 10 November 2016
We consider the non-minimal model of gravity in Y(R) F2-form. We investigate a particular case of the model, for which the higher order derivatives are eliminated but the scalar curvature R is kept…
Some Anisotropic Universes in the Presence of Imperfect Fluid Coupling with Spatial Curvature
- Özgür Akarsu, C. Kılınç
- Mathematics, Physics
- 15 August 2010
We consider Bianchi VI spacetime, which also can be reduced to Bianchi types VI0-V-III-I. We initially consider the most general form of the energy-momentum tensor which yields anisotropic stress and…
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