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West Bengal, India

Paul B.C.,North Bengal University | Thakur P.,Alipurduar College | Verma M.M.,University of Lucknow
Pramana - Journal of Physics | Year: 2013

Cosmological models with modified Chaplygin gas (MCG) in the framework of Horava-Lifshitz (HL) theory of gravity, both with and without detailed balance, are obtained. The equation of state (EOS) for a MCG contains three unknown parameters namely, A, α, B. The allowed values of some of these parameters of the EOS are determined using the recent astrophysical and cosmological observational data. Using observational data from H(z)-z, baryon acoustic oscillation (BAO) peak parameter and cosmic microwave background (CMB) shift parameter we study cosmologies in detailed-balance and beyond detailed-balance scenario. In this paper we take up the beyond detailed-balance scenario in totality and contribution of dark radiation in detailedbalance scenario on the parameters of the EOS. We explore the effect of dark radiation on the whole range of the effective neutrino parameter (ΔNν) to constrain matter contributing parameter B in both the detailed-balance and the beyond detailed-balance scenarios. It has been observed that greater the dark radiation less the matter contribution in the MCG in both the scenario considered here. In order to check the validity of beyond detailed-balance scenario we plot supernovae magnitudes (μ) with red-shift of Union 2 data and then the variation of state parameter with redshift is studied. It is noted that beyond detailed-balance scenario is suitable for cosmological model in HL gravity with MCG. © 2013 Indian Academy of Sciences. Source

Paul B.C.,North Bengal University | Thakur P.,Alipurduar College
Journal of Cosmology and Astroparticle Physics | Year: 2013

We investigate the linear growth function for the large scale structures of the universe considering modified Chaplygin gas as dark energy. Taking into account observational growth data for a given range of redshift from the Wiggle-Z measurements and rms mass fluctuations from Ly-α measurements we numerically analyze cosmological models to constrain the parameters of the MCG. The observational data of Hubble parameter with redshift z is also considered. The Wang-Steinhardt ansatz for growth index γ and growth function f (defined as f = Ωmγ(a)) are considered for the numerical analysis. The best-fit values of the equation of state parameters obtained here is employed to study the growth function (f), growth index (γ) and equation of state (ω) with redshift z. The observational constraints on MCG parameters obtained here are compared with that of the GCG model for viable cosmology. It is noted that MCG also satisfactorily accommodates an accelerating phase followed by a matter dominated phase of the universe. © 2013 IOP Publishing Ltd and Sissa Medialab srl. Source

Paul B.C.,North Bengal University | Thakur P.,Alipurduar College | Saha A.,Jalpaiguri Government Engineering College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We present cosmological models with modified Chaplygin gas (MCG) in the framework of Horava-Lifshitz (HL) theory of gravity. The equation of state (EOS) for a MCG is a three-variable equation determined by A, α, B. The allowed values of these parameters of the EOS are determined using the recent astrophysical and cosmological observational data. For this we consider H(z)-z, BAO peak, CMB shift parameter data to obtain a suitable range of values of the parameters for a viable cosmological model. Considering the suitable range of effective neutrino parameter (ΔN ν), the ranges of values of the B-parameter along with A S (defined by A, α, and B) and α are determined here by chi-square minimization. © 2012 American Physical Society. Source

Pal B.B.,Kalyani University | Kumar M.,Alipurduar College
Advances in Intelligent Systems and Computing | Year: 2014

This paper presents an extended version of goal programming (GP) approach for modeling and solving farm planning problems having objectives with interval parameter sets by utilizing farming resources in the planning horizon. In the model formulation of the problem, the defined goals with interval parameters are converted into conventional goals by using interval arithmetic technique in interval programming and introducing under- and over-deviational variables to each of them. In the decision process, extended GP (EGP) approach, i.e. convex combination of both the modelling aspects, minsum GP and minmax GP are addressed in the achievement function for minimizing the possible regret towards goal achievement from the optimistic point of view in the inexact decision making environment. The potential use of the approach is demonstrated via a case example. Source

Ghosh S.,Jadavpur University | Das Burman A.,Indian Association for The Cultivation of Science | De G.C.,Alipurduar College | Das A.R.,Indian Association for The Cultivation of Science
Journal of Physical Chemistry B | Year: 2011

Interfacial and bulk properties of sodium dodecyl sulfate (SDS), polyoxyethylene (20) sorbitan monooleate (Tween-80), and their binary mixtures in aqueous medium have been investigated using surface tension, conductance, and fluorescence measurements at different temperatures. The critical micelle concentration (CMC), counterion binding, polarity index, aggregation number, thermodynamics of interfacial adsorption, and micellization are evaluated. The entropic contribution is found to be the predominant factor in micelle formation. The aggregation number and the polarity index of the micelle interior estimated by the pyrene fluorescence technique show interesting temperature dependence. The size and composition of the mixed micelles vary with the total concentration. The micellar compositions, activities of the individual components in the mixed species, and intersurfactant interactions are also estimated following regular solution theory, excess thermodynamic functions, and a molecular thermodynamic model. The surfactant mixtures are found to be nonideal with a lower degree of counterion binding compared to the individual members. Mixed micelles are nonspherical in nature at all temperatures when the mole fraction (α) of the ionic part in mixtures is high but transform to spherical when αSDS is ≥0.50. © 2011 American Chemical Society. Source

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