Rize, Turkey
Rize, Turkey

Time filter

Source Type

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.


Nayak B.,Utkal University | Jamil M.,National University of Sciences and Technology | Jamil M.,Eurasian University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We study the evolution of primordial black holes by considering present universe is no more matter dominated rather vacuum energy dominated. We also consider the accretion of radiation, matter and vacuum energy during respective dominance period. In this scenario, we found that radiation accretion efficiency should be less than 0.366 and accretion rate is much larger than previous analysis by Nayak et al. (2009) [1]. Thus here primordial black holes live longer than previous works Nayak and Singh (2011) [1]. Again matter accretion slightly increases the mass and lifetime of primordial black holes. However, the vacuum energy accretion is slightly complicated one, where accretion is possible only up to a critical time. If a primordial black hole lives beyond critical time, then its' lifespan increases due to vacuum energy accretion. But for presently evaporating primordial black holes, critical time comes much later than their evaporating time and thus vacuum energy could not affect those primordial black holes. © 2012 Elsevier B.V.


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.


Myrzakulov R.,Eurasian University | Myrzakulov R.,California State University, Fresno
European Physical Journal C | Year: 2011

It is shown that the acceleration of the universe can be understood by considering a F(T) gravity models. For these F(T) gravity models, a variant of the accelerating cosmology reconstruction program is developed. Some explicit examples of F(T) are reconstructed from the background FRW expansion history. © 2011 Springer-Verlag / Società Italiana di Fisica.


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.


Myrzakulov R.,Eurasian University | Sebastiani L.,Eurasian University
General Relativity and Gravitation | Year: 2015

In this paper we analyze spherically symmetric static vacuum solutions with various topologies in mimetic gravity. When the Einstein’s tensor is different from zero, a new class of solutions different from the Schwarzschild one emerges from the theory. We analyze the feature of the new solutions and we study the planar motion for the spherical case. © 2015, Springer Science+Business Media New York.


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.


Myrzakulov R.,Eurasian University
Entropy | Year: 2012

This a brief review on F(T) gravity and its relation with k-essence. Modified teleparallel gravity theory with the torsion scalar has recently gained a lot of attention as a possible explanation 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, and deduce the required conditions for the equivalence between of F(T) models with pure kinetic k-essence models. We present a new class of models of F(T)-gravity and k-essence. © 2012 by the author.


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.


Sebastiani L.,Eurasian University | Myrzakulov R.,Eurasian University
International Journal of Geometric Methods in Modern Physics | Year: 2015

In this short review, we revisit inflation in F(R)-gravity. We find several F(R)-models for viable inflation by applying some reconstruction techniques. A special attention is payed in the reproduction of the last Planck satellite data. The possible generalizations of Starobinsky-like inflation are found and discussed. The early-time acceleration is analyzed in a higher derivative quantum gravitational model which mainly reduces to F(R)-gravity. © 2015 World Scientific Publishing Company.

Loading Eurasian University collaborators
Loading Eurasian University collaborators