Attractor Solutions in f(T) Cosmology

In this paper, we explore the cosmological implications of interacting dark energy model in a torsion based gravity namely $f(T)$. Assuming dark energy interacts with dark matter and radiation components, we examine the stability of this model by choosing different forms of interaction terms. We consider three different forms of dark energy: cosmological constant, quintessence and phantom energy. We then obtain several attractor solutions for each dark energy model interacting with other components. This model successfully explains the coincidence problem via the interacting dark energy scenario.Comment: 10 pages, 23 figures, version accepted for publication in European Physical Journal C (2012

Comment on Ricci Collineations of Static Spherically Symmetric Spacetimes

We present a counter example to a theorem given by Amir {\em et al.} J. Math. Phys. {\bf 35}, 3005 (1994). We also comment on a misleading statements of the same reference.Comment: 4 pages,LaTex fil

Thermodynamics of interacting entropy-corrected holographic dark energy in a non-flat FRW universe

A so-called "entropy-corrected holographic dark energy" (ECHDE), was recently proposed to explain the dark energy-dominated universe with the help of quantum corrections to the entropy-area relation in the setup of loop quantum cosmology. Using this new definition, we investigate its thermodynamical features including entropy and energy conservation. We describe the thermodynamical interpretation of the interaction between ECHDE and dark matter in a non-flat universe. We obtain a relation between the interaction term of the dark components and thermal fluctuation. Our study further generalizes the earlier works [M.R. Setare and E.C. Vagenas, Phys. Lett. B 666 (2008) 111; B. Wang et al., Phys. Lett. B 662 (2008) 1] in this direction.Comment: 14 pages, no figure, accepted by Int. J. Mod. Phys.

Pengaruh Model Pembelajaran Kooperatif Tipe Make a Match Terhadap Nilai Kerjasama Dan Hasil Belajar Kognitif Kimia Siswa Kelas X Sman 1 Bambanglipuro Bantul

Cooperation value and students\u27 cognitive learning outcomes were examined as the effect of the implementation of cooperative learning – make a match. The Nonequivalent Control Pre-test dan Post-test Group Design as this quasi-experimental research was involved 1st grade students of SMAN 1 Bambanglipuro at academic year 2013/2014. Students at X4 as an experimental sampel and X3 as a control sampel were choosen by cluster random sampling technique. The data was collected using pre-test and post-test for hydrocarbon subject matter, cooperation scale, and observation scale, was then analyzed by t-test. The result shows there was no significant effect of cooperative learning – make a match toward to students\u27 cooperation value and cognitive learning outcomes, were proven by sig. (2-tailed) of t-test > 0.05 at 0.282 and sig. (2-tailed) of MannWhitney test > 0.05 at 0.953 respectively

Teleparallel Killing Vectors of the Einstein Universe

In this short paper we establish the definition of the Lie derivative of a second rank tensor in the context of teleparallel theory of gravity and also extend it for a general tensor of rank $p+q$. This definition is then used to find Killing vectors of the Einstein universe. It turns out that Killing vectors of the Einstein universe in the teleparallel theory are the same as in General Relativity.Comment: 9 pages, accepted for publication in Mod. Phys. Lett.

Accretion of non-minimally coupled generalized Chaplygin gas into black holes

The mass evolution of Schwarzschild black holes by the absorption of scalar fields is investigated in the scenario of the generalized Chaplygin gas (GCG). The GCG works as a unification picture of dark matter plus dark energy that naturally accelerates the expansion of the Universe. Through elements of the quasi-stationary approach, we consider the mass evolution of Schwarzschild black holes accreted by non-minimally coupled cosmological scalar fields reproducing the dynamics of the GCG. As a scalar field non-minimally coupled to the metrics, such an exotic content has been interconnected with accreting black holes. The black hole increasing masses by the absorption of the gas reflects some consistence of the accretion mechanism with the hypothesis of the primordial origin of supermassive black holes. Our results effectively show that the non-minimal coupling with the GCG dark sector accelerates the increasing of black hole masses. Meanwhile some exotic features can also be depicted for specific ranges of the non-minimal coupling in which the GCG dynamics is substantially modified.Comment: 13 pages, 03 figure

Potentiality of the Usage of Compressed Natural Gas for Competitiveness in Service Delivery Industries

. With the rising costs of gasoline, many vehicle owners are looking for alternatives of it. Compressed natural gas (CNG) has been tested for this very purpose in some countries and found as a better alternative so far. CNG comes from country's natural resources and it is clean and less costly to use. This paper is mainly an analysis of the potential benefits of using natural gas as a transportation fuel by the service delivery industries. It will examine CNG's potential contribution in reducing delivery and vehicle maintenance cost, saving money in the long run projects, improving fuel efficiency, enhancing physical safety and assuring environment friendly emissions of carbon monoxide or reactive gases for the service delivery industries

Financing Small and Medium Enterprises in Bangladesh – Issues and Challenges

. Now-a-days, Small and Medium Enterprises (SMEs) have become an important sector that is supposed to play a pivotal role in boosting the economy of Bangladesh. But, SME financing is still facing some remarkable challenges that limit its potential success in contributing to the economy. Lots of thinking has contributed to the initiation and development of SMEs in Bangladesh. Now is the time to identify the challenges and making adjustments to the initial thinking. This paper is, therefore, an attempt to analyze various issues and challenges of financing this particular sector and find some worthy ways out to overcome these challenges. It will also survey various literatures and reports on the concerned field and recommend supporting actions to help this highly prospective industrial sector operate in a fully yielding manner

Notes on dark energy interacting with dark matter and unparticle in loop quantum cosmology

We investigate the behavior of dark energy interacting with dark matter and unparticle in the framework of loop quantum cosmology. In four toy models, we study the interaction between the cosmic components by choosing different coupling functions representing the interaction. We found that there are only two attractor solutions namely dark energy dominated and dark matter dominated Universe. The other two models are unstable, as they predict either a dark energy filled Universe or one completely devoid of it.Comment: 9 pages, 10 figures. v2: Minor revisions, matches published versio