• P K Chattopadhyay

      Articles written in Pramana – Journal of Physics

    • Investigation of the boundary value problem corresponding to a generalized Skyrme lagrangian

      Rajesh Kumar P K Chattopadhyay

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      A detailed numerical analysis of the boundary value problem resulting from the most general Skyrme type lagrangian containing up to quartic terms in field gradients is presented. The additional parameters in the lagrangian can be related to pion-pion scattering lengths. It is found that solutions to the boundary value problem does not exist for all values of the parameters and in particular, for the values predicted from pion-pion scattering data. Physical quantities of the nucleon are calculated for the highest possible values of the parameters admitting a solution and are compared with the corresponding values for the Skyrme model and experimental values.

    • The breaking of O(6) symmetry in 118Xe and 120Xe

      Bir Singh Rawat P K Chattopadhyay

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      The spectra of the isotopes of xenon are analysed from the point of view of O(6) symmetry breaking. It is pointed out that the excitation energies of the states 03+ can be used in detecting breaking of the symmetry. The nature of symmetry breaking in 118Xe and 120Xe is indicated.

    • Complex plasma experimental device – A test bed for studying dust vortices and other collective phenomena


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      A typical device for carrying out sophisticated and complex dusty plasma experiments is designed, fabricated and made operational at the Institute for Plasma Research, India. The device is named as complex plasma experimental device (CPED). The main aim of this multipurpose machine is to study the formation and behaviour of dust vortices in the absence of external magnetic field under the effect of various plasma parameters. Further, the device is equipped with advanced imaging diagnostics for studying many other interesting phenomena such as dust oscillations, three-dimensional crystalline structures, dust rotation, etc. The device is quite flexible to accommodate many innovative experiments. Detailed design of the device, its diagnostics capabilities and theadvanced image analysis techniques are presented in this paper.

    • Anisotropic compact star in modified Vaidya–Tikekar model admitting new solutions and maximum mass


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      In this paper, we try to demonstrate a method to generate new class of exact solutions to the Einstein’s field equations (EFE) by introducing a new parameter (κ) in the Vaidya–Tikekar metric ansatz describing a static spherically symmetric relativistic star having anisotropic fluid pressure. We particularly obtained solutions in closed form in terms of trigonometric functions. Introduction of a new parameter in the metric ansatz predicts some interesting results. In our formalism, the main feature of the new class of solutions is that one can study the effects of the new parameter (κ) on different physical parameters of a compact object such as its mass, radius, surface redshift etc. Moreover, if we switch off the new parameter (κ = 0), it also gives new realistic solutions which arethe modified version of isotropic Matese–Whitman solutions in the presence of pressure anisotropy. Consequently, we present here that a plethora of well-known stellar solutions can be identified as sub-class (κ = ±1) of ourclass of solutions. We predict here the maximum mass of compact object in isotropic case and also in the presence of pressure anisotropy. The central density is found to be as high as ∼10$^{15}$ gm/cc and thus the present model is capable enough to accommodate a wider class of compact objects. We examine the physical viability of solutions for studying relativistic compact stars and it is found that all the stability conditions are satisfied.

    • Effect of charge on the maximum mass of the anisotropic strange quark star


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      In this article, we have studied the solutions of Einstein–Maxwell field equations for compact objects in the presence of net electric charge. Interior physical 3-space is defined by Vaidya–Tikekar metric in spheroidal geometry. The metric is characterised by two parameters, namely, spheroidal parameter K and curvature parameter R. The nature of the interior fluid is considered to be anisotropic. Assuming strange matter equation of state (EOS)in the MIT Bag model for the interior matter content, namely, p = $\frac{1}{3}$(ρ − 4 B), where B is the Bag constant, we determine various physical properties of the charged compact star. We have taken the value of surface density ρs(= 4 B) as a probe to evaluate the mass–radius relation for the compact star in the presence of net electric charge and using the range of B necessary for possible stable strange matter. It is interesting to note that in this model thereexist a maximum radius of a star which depends on B. We further note that compactness of the star corresponding to the maximum radius always lies below the Buchdahl limit ($\le$$\frac{4}{9}$) for the maximum allowed value of the pressure anisotropy and electromagnetic field. Energy and causality conditions hold good throughout the star in the presence of charge also. Prediction of mass of the strange stars is possible in the present model. We have determined mass, radius, surface red-shift and other relevant physical parameters of the compact objects.

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