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Myrzakulov R.,Eurasian University
European Physical Journal C | Year: 2012

In this paper, we consider a theory of gravity with a metric-dependent torsion namely the F(R,T) gravity, where R is the curvature scalar and T is the torsion scalar. We study the geometric root of such theory. In particular we give the derivation of the model from the geometrical point of view. Then we present the more general form of F(R,T) gravity with two arbitrary functions and give some of its particular cases. In particular, the usual F(R) and F(T) gravity theories are particular cases of the F(R,T) gravity. In the cosmological context, we find that our new gravitational theory can describe the accelerated expansion of the Universe. © 2012 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica. Source


Nojiri S.,Nagoya University | Odintsov S.D.,Consejo Superior de Investigaciones Cientificas | Odintsov S.D.,Catalan Institution for Research and Advanced Studies | Odintsov S.D.,Eurasian University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We propose a bigravity analogue of the F(R) gravity. Our construction is based on recent ghost-free massive bigravity where additional scalar fields are added and the corresponding conformal transformation is implemented. It turns out that F(R) bigravity is easier to formulate in terms of the auxiliary scalars as the explicit presentation in terms of F(R) is quite cumbersome. The consistent cosmological reconstruction scheme of F(R) bigravity is developed in detail, showing the possibility to realize nearly arbitrary physical universe evolution with consistent solution for second metric. The examples of accelerating universe which includes phantom, quintessence and ΛCDM acceleration are worked out in detail and their physical properties are briefly discussed. © 2012 Elsevier B.V. Source


Iskender E.,Karadeniz Technical University | Aksoy A.,Eurasian University
Construction and Building Materials | Year: 2012

The purpose of this study is to compare laboratory and field performances for dense graded asphalt mixtures. Control road pavement section was constructed in Black Sea Coast Highway. Marshall identical control samples produced in laboratory and core samples taken from wearing courses before the traffic opened were used. Three different moisture conditioning methods were applied to control laboratory and core samples. Mechanical properties of samples were evaluated with indirect tension, indirect tension strength and repeated creep tests. Indirect tensile strength test results for laboratory mixtures were found 1.22 and 1.30 times more in accordance with field samples at 10 °C and 20 °C respectively. Marshall samples gave higher resilient modulus for all control and conditioned mixtures. Repeated creep test results also proved the difference between laboratory and field sample performance. Laboratory samples protected their structural integrity along with the test duration and did not showed tertiary creep. It is concluded from this study that laboratory samples state expressly higher performance according to the core field samples. © 2011 Elsevier Ltd. All rights reserved. Source


Myrzakulov R.,Eurasian University
Advances in High Energy Physics | Year: 2012

We investigate the trefoil and figure eight knot universes from Bianchi type I cosmology. In particular, we construct several concrete models describing the knot universes related to the cyclic universe and examine those cosmological features and properties in detail. Finally some examples of unknotted closed curves solutions (spiky and Mobius strip universes) are presented. © 2012 Ratbay Myrzakulov. Source


Myrzakulov R.,Eurasian University
General Relativity and Gravitation | Year: 2012

Modified teleparallel gravity theory with the torsion scalar has recently gained a lot of attention as a possible candidate of dark energy. We perform a thorough reconstruction analysis on the so-called F(T) models, where F(T) is some general function of the torsion term. We derive conditions for the equivalence between of F(T) models with purely kinetic k-essence. We present a new class models of F(T) gravity and k-essence. © 2012 Springer Science+Business Media, LLC. Source

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