Black hole solutions correspondence between conformal and massive theories of gravity

In this work, a correspondence between black hole solutions of conformal and massive theories of gravity is found. It is seen that this correspondence imposes some constraints on parameters of these theories. What is more, a relation between the mass of black holes and the parameters of massive gravity is found. Indeed, the acceptable ranges of massive gravity parameters ($c_{1}$\ and $c_{2}$) are found. It is shown that by considering the positive mass of black holes, some ranges of $c_{1}$\ and $c_{2}$ are acceptable.Comment: 7 pages, 1 figur

Einstein-Born-Infeld-Massive Gravity: adS-Black Hole Solutions and their Thermodynamical properties

In this paper, we study massive gravity in the presence of Born-Infeld nonlinear electrodynamics. First, we obtain metric function related to this gravity and investigate the geometry of the solutions and find that there is an essential singularity at the origin ($r=0$). It will be shown that due to contribution of the massive part, the number, types and places of horizons may be changed. Next, we calculate the conserved and thermodynamic quantities and check the validation of the first law of thermodynamics. We also investigate thermal stability of these black holes in context of canonical ensemble. It will be shown that number, type and place of phase transition points are functions of different parameters which lead to dependency of stability conditions to these parameters. Also, it will be shown how the behavior of temperature is modified due to extension of massive gravity and strong nonlinearity parameter. Next, critical behavior of the system in extended phase space by considering cosmological constant as pressure is investigated. A study regarding neutral Einstein-massive gravity in context of extended phase space is done. Geometrical approach is employed to study the thermodynamical behavior of the system in context of heat capacity and extended phase space. It will be shown that GTs, heat capacity and extended phase space have consistent results. Finally, critical behavior of the system is investigated through use of another method. It will be pointed out that the results of this method is in agreement with other methods and follow the concepts of ordinary thermodynamics.Comment: 19 pages with 17 figures, Sections V, VI, VII, VIII with related figures and discussions are added. arXiv admin note: text overlap with arXiv:1507.0656

Magnetic branes in Gauss-Bonnet gravity with nonlinear electrodynamics: correction of magnetic branes in Einstein-Maxwell gravity

In this paper, we are considering two first order corrections to both gravity and gauge sides of the Einstein-Maxwell gravity: Gauss-Bonnet gravity and quadratic Maxwell invariant as corrections. We obtain horizonless magnetic solutions by implying a metric which representing a topological defect. We analyze the geometric properties of the solutions and investigate the effects of both corrections, and find that these solutions may be interpreted as the magnetic branes. We study the singularity condition and find a nonsingular spacetime with a conical geometry. We also investigate the effects of different parameters on deficit angle of spacetime near the origin.Comment: 10 pages with 9 figure

Contraction of cold neutron star due to in the presence a quark core

Motivated by importance of the existence of quark matter on structure of neutron star. For this purpose, we use a suitable equation of state (EoS) which include three different parts: i) a layer of hadronic matter, ii) a mixed phase of quarks and hadrons, and, iii) a strange quark matter in the core. For this system, in order to do more investigation of the EoS, we evaluate energy, Le Chatelier's principle and stability conditions. Our results show that the EoS satisfies these conditions. Considering this EoS, we study the effect of quark matter on the structure of neutron stars such as maximum mass and the corresponding radius, average density, compactness, Kretschmann scalar, Schwarzschild radius, gravitational redshift and dynamical stability. Also, considering the mentioned EoS in this paper, we find that the maximum mass of hybrid stars is a little smaller than that of the corresponding pure neutron star. Indeed the maximum mass of hybrid stars can be quite close to the pure neutron stars. Our calculations about the dynamical stability show that these stars are stable against the radial adiabatic infinitesimal perturbations. In addition, our analyze indicates that neutron stars are under a contraction due to the existence of quark core.Comment: 10 pages, 3 figures, 4 table

Exploring patterns in teachers’ conceptions of citizenship and political participation: A survey of secondary school teachers in Karachi, Pakistan

This paper examines patterns in teachers’ understanding of conceptual and practical aspects of citizenship by analyzing survey data obtained from 320 teachers of public and private sector secondary schools in Karachi, Pakistan. The survey was conducted using a five-point-Likert scale ranging from ‘strongly disagree through ‘neutral’ to ‘strongly-agree’ and openended questions on citizen participation in politics. The survey questionnaire included 28 items that reflected various aspects of citizen rights and responsibilities. Principal Component Analysis (PCA)) showed several patterns in teacher’s conceptions of citizenship with reference to democratization. The analysis demonstrates that teachers’ conception of citizenship is shaped by confusions and contradictions in terms of their understanding of citizen rights and responsibilities wherein they conceptualized a passive and apolitical role for citizens. Nevertheless, the teachers also express dissatisfaction with quality of people’s participation in politics in the contemporary context of Pakistan. The study offers insights into teachers’ constructions of citizenship and highlight implications for the project of citizenship education in particular and democratization in general in the context of Pakistan

Performance Comparison of the mathematical skills of Computer and Electronics students in the Chamran college technical rasht

The aim of this research paper is to study about chamran college technical Rasht student's skills in math lesson according to Bloom's recognition compasses. Statistical samples were 72 students (males) from computer and Electronics branches of technical major who answered math questions from whatever they had learned before  entering the university. The Exam included 50 multiple choice questions which were designed and classified due to Benjamin Bloom's recognition compasses, Results show that: a) Students had the best performance in science, application, comprehension  and knowledge, but they had the least performance in evaluation and judgment, analysis and combination