Government Training College

Hugli, India

Government Training College

Hugli, India
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Chakraborty K.,Government Training College | Rahaman F.,Jadavpur University | Mallick A.,Jadavpur University
Modern Physics Letters A | Year: 2017

We propose a relativistic model of compact star admitting conformal symmetry. Quark matter and baryonic matter which are considered as two different fluids, constitute the star. We define interaction equations between the normal baryonic matter and the quark matter and study the physical situations for repulsive, attractive and zero interaction between the constituent matters. The measured value of the Bag constant is used to explore the spacetime geometry inside the star. From the observed values of the masses of some compact objects, we have obtained theoretical values of the radii. Theoretical values of the radii match well with the previous predictions for such compact objects. © 2017 World Scientific Publishing Company.


Rahaman F.,Jadavpur University | Kuhfittig P.K.F.,Milwaukee School of Engineering | Chakraborty K.,Government Training College | Usmani A.A.,Aligarh Muslim University
General Relativity and Gravitation | Year: 2012

This paper discusses the observed flat rotation curves of galaxies in the context of noncommutative geometry. The energy density of such a geometry is diffused throughout a region due to the uncertainty encoded in the coordinate commutator. This intrinsic property appears to be sufficient for producing stable circular orbits, as well as attractive gravity, without the need for dark matter. © 2011 Springer Science+Business Media, LLC.


Sana S.,Government Training College | Chattopadhyay K.N.,University of Burdwan
Journal of Chemical Education | Year: 2015

Chunk-based strategy and mnemonics have been developed to write ground state electron configurations of elements, which is a routine exercise for the higher secondary (pre-university) level general chemistry students. To assimilate a better understanding of the nature of chemical reactions, an adequate knowledge of the periodic table of elements is mandatory. Valence shell electrons of elements participate in redox chemical reactions. Chemistry students thus must be able to write electron configurations correctly. Here we have explored a chunking tool for determining the electron configurations of elements having atomic numbers up to 120. © 2015 The American Chemical Society and Division of Chemical Education, Inc.


Chakraborty K.,Government Training College | Rahaman F.,Jadavpur University | Nandi A.,Government Training College | Islam N.,Danga High Madrasa
General Relativity and Gravitation | Year: 2014

Observed rotational curves of neutral hydrogen clouds strongly support the fact that galactic halo contains huge amount of nonluminous matter, the so called gravitational dark matter. The nature of dark matter is a point of debate among the researchers. Recent observations reported the presence of ions of O, S, C, Si etc. in the galactic halo and intergalactic medium. This supports the possibility of existence of electric field in the galactic halo region. We therefore propose a model of galactic halo considering this electric field arising due to charged particles as one of the inputs for the background spacetime metric. Considering dark matter as an anisotropic fluid we obtain the expressions for energy density and pressure of dark matter there and consequently the equation of state of dark matter. Various other aspects of the solutions are also analyzed along with a critical comparison with and constraints of different observational evidences. © 2014, Springer Science+Business Media New York.


Rahaman F.,Jadavpur University | Jafry A.K.,Shibpur Dinobundhoo Institution | Chakraborty K.,Government Training College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We extend the Krori-Barua analysis of the static, spherically symmetric, Einstein-Maxwell field equations and consider charged fluid sources with anisotropic stresses. The inclusion of a new variable (tangential pressure) allows the use of a nonlinear, Chaplygin-type equation of state with coefficients fixed by the matching conditions at the boundary of the source. Some physical features are briefly discussed. © 2010 The American Physical Society.


Varela V.,University of Aberdeen | Rahaman F.,Jadavpur University | Chakraborty K.,Government Training College | Kalam M.,Netaji Nagar College for Women
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

Ivanov pointed out substantial analytical difficulties associated with self-gravitating, static, isotropic fluid spheres when pressure explicitly depends on matter density. Simplifications achieved with the introduction of electric charge were noticed as well. We deal with self-gravitating, charged, anisotropic fluids and get even more flexibility in solving the Einstein-Maxwell equations. In order to discuss analytical solutions we extend Krori and Barua's method to include pressure anisotropy and linear or nonlinear equations of state. The field equations are reduced to a system of three algebraic equations for the anisotropic pressures as well as matter and electrostatic energy densities. Attention is paid to compact sources characterized by positive matter density and positive radial pressure. Arising solutions satisfy the energy conditions of general relativity. Spheres with vanishing net charge contain fluid elements with unbounded proper charge density located at the fluid-vacuum interface. Notably the electric force acting on these fluid elements is finite, although the acting electric field is zero. Net charges can be huge (1019C) and maximum electric field intensities are very large (1023-1024statvolt/cm) even in the case of zero net charge. Inward-directed fluid forces caused by pressure anisotropy may allow equilibrium configurations with larger net charges and electric field intensities than those found in studies of charged isotropic fluids. Links of these results with charged strange quark stars as well as models of dark matter including massive charged particles are highlighted. The van der Waals equation of state leading to matter densities constrained by cubic polynomial equations is briefly considered. The fundamental question of stability is left open. © 2010 The American Physical Society.


Rahaman F.,Jadavpur University | Jamil M.,National University of Sciences and Technology | Chakraborty K.,Government Training College
Astrophysics and Space Science | Year: 2010

Motivated by earlier studies (Tiwari et al. in Astrophys. Space Sci. 182:105, 1984; Herrera and Varela in Phys. Lett. 189:11, 1994), we model electron as a spherically symmetric charged perfect fluid distribution of matter. The existing model is extended assuming a matter source that is characterized by quadratic equation of state in the context of general theory of relativity. For the suitable choices of the parameters, our charged fluid models almost satisfy the physical properties of electron. © 2010 Springer Science+Business Media B.V.


Rahaman F.,Jadavpur University | Jamil M.,National University of Sciences and Technology | Sharma R.,St. Joseph's College | Chakraborty K.,Government Training College
Astrophysics and Space Science | Year: 2010

We provide a new class of interior solutions for anisotropic stars admitting conformal motion. The Einstein's field equations in this construction are solved for specific choices of the density/mass functions. We analyze the behavior of the model parameters like radial and transverse pressures, density and surface tension. © Springer Science+Business Media B.V. 2010.


Rahaman F.,Jadavpur University | Nandi K.K.,North Bengal University | Bhadra A.,North Bengal University | Kalam M.,Netaji Nagar College for Women | Chakraborty K.,Government Training College
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

Taking the flat rotation curve as input and treating the matter content in the galactic halo region as perfect fluid we obtain a space-time metric at the galactic halo region in the framework of general relativity. We find that the resultant space-time metric is a non-relativistic dark matter induced space-time embedded in a static Friedmann-Lemaître-Robertson-Walker universe i.e. the flat rotation curve not only leads to the existence of dark matter but also suggests about the background geometry of the universe. Within its range of validity the flat rotation curve and the demand that the dark matter to be non-exotic together indicate for a (nearly) flat universe as favored by the modern cosmological observations. We obtain the expressions for energy density and pressure of dark matter there and consequently the equation of state of dark matter. Various other aspects of the solutions are also analyzed. © 2010 Elsevier B.V.


Rahaman F.,Jadavpur University | Jamil M.,National University of Sciences and Technology | Ghosh A.,Jadavpur University | Chakraborty K.,Government Training College
Modern Physics Letters A | Year: 2010

In this paper, we have presented an algorithm to generate various black hole solutions in general relativity and alternative theories of gravity. The algorithm involves few dimensional parameters that are assigned suitable values to specify the required black hole. © 2010 World Scientific Publishing Company.

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