• Volume 61, Issue 4

      October 2003,   pages  633-778 and C779-C783

    • Second invariant for two-dimensional classical super systems

      S C Mishra Roshan Lal Veena Mishra

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      Construction of superpotentials for two-dimensional classical super systems (forN > 2) is carried out. Some interesting potentials have been studied in their super form and also their integrability.

    • What price the spin-statistics theorem?

      E C G Sudarshan I M Duck

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      We examine a number of recent proofs of the spin-statistics theorem. All, of course, get the target result of Bose-Einstein statistics for identical integral spin particles and Fermi-Dirac statistics for identical half-integral spin particles. It is pointed out that these proofs, distinguished by their purported simple and intuitive kinematic character, require assumptions that are outside the realm of standard quantum mechanics. We construct a counterexample to these non-dynamical kinematic ‘proofs’ to emphasize the necessity of a dynamical proof as distinct from a kinematic proof. Sudarshan’s simple non-relativistic dynamical proof is briefly described. Finally, we make clear the price paid for any kinematic ‘proof’.

    • On Bianchi-I cosmic strings coupled with Maxwell fields in bimetric relativity

      V Mahurpawar S D Deo

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      Axially symmetric Bianchi-I model is studied with source cosmic cloud strings coupled with electromagnetic field in Rosen’s bimetric theory of relativity and observed that there is no contribution from cosmic strings and Maxwell fields in this theory.

    • Radial oscillations of magnetized proto strange stars in temperature- and density-dependent quark mass model

      V K Gupta Asha Gupta S Singh J D Anand

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      We report on the study of the mass-radius (M–R) relation and the radial oscillations of magnetized proto strange stars. For the quark matter we have employed the very recent modification, the temperature- and density-dependent quark mass model of the well-known density-dependent quark mass model. We find that the effect of magnetic field, both on the maximum mass and radial frequencies, is rather small. Also a proto strange star, whether magnetized or otherwise, is more likely to evolve into a strange star rather than transform into a black hole.

    • Anisotropic cosmological models and generalized scalar tensor theory

      Subenoy Chakraborty Batul Chandra Santra Nabajit Chakravarty

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      In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely, axially symmetric Bianchi-I, Bianchi-III and Kortowski-Sachs space-time. For bulk viscous fluid, both exponential and power-law solutions have been studied and some assumptions among the physical parameters and solutions have been discussed.

    • Quantum molecular dynamics approach to estimate spallation yield fromp +208Pb reaction at 800 MeV

      P K Sarkar Maitreyee Nandy

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      The spallation yield of neutrons and other mass fragments produced in 800 MeV proton induced reaction on208Pb have been calculated in the framework of quantum molecular dynamics (QMD) model. The energy spectra and angular distribution have been calculated. Also, multiplicity distributions of the emitted neutrons and kinetic energy carried away by them have been estimated and compared with the available experimental data. The agreement is satisfactory. A major contribution to the neutron emission comes from statistical decay of the fragments. For mass and charge distributions of spallation products the QMD process gives rise to target-like and projectile-like fragments only.

    • Differential and integral cross-sections of e-O2, O3, NO, CO scattering at energies 100–1000 eV

      P M Patel K N Joshipura

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      A modified additivity rule is formulated to calculate the differential cross-sections for elastic scattering of electrons from molecules. It improves the results at small angles and at relatively lower incident energies (<1000 eV). Integral cross-sections calculated presently are combined with the known total ionization cross-sections to obtain total (complete) cross-sections. An extension of the present approximation to larger molecules is also suggested.

    • Non-linear propagation of laser beam and focusing due to self-action in optical fiber: Non-paraxial approach

      R K Khanna R C Chouhan

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      A somewhat more general analysis for solving spatial propagation characteristics of intense Gaussian beam is presented and applied to the laser beam propagation in step-index profile as well as parabolic profile dielectric fibers with Kerr non-linearity. Considering self-action due to saturating and non-saturating non-linearity in the refractive index, a general theory has been developed without any kind of power series expansion for the dielectric constant as is usually done in other theories that make use of paraxial approximation. Result of the steady state self-focusing analysis indicates that the Kerr non-linearity acts as a perturbation on the radial inhomogeneity due to fiber geometry. Analysis indicates that the paraxial rays and peripheral rays focus at different points, indicating aberration effect. Calculated critical power matches with the experimentally reported result.

    • Energy fluxes in helical magnetohydrodynamics and dynamo action

      Mahendra K Verma

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      Renormalized viscosity, renormalized resistivity, and various energy fluxes are calculated for helical magnetohydrodynamics using perturbative field theory. The calculation is of firstorder in perturbation. Kinetic and magnetic helicities do not affect the renormalized parameters, but they induce an inverse cascade of magnetic energy. The sources for the large-scale magnetic field have been shown to be (1) energy flux from large-scale velocity field to large-scale magnetic field arising due to non-helical interactions and (2) inverse energy flux of magnetic energy caused by helical interactions. Based on our flux results, a primitive model for galactic dynamo has been constructed. Our calculations yield dynamo time-scale for a typical galaxy to be of the order of 108 years. Our field-theoretic calculations also reveal that the flux of magnetic helicity is backward, consistent with the earlier observations based on absolute equilibrium theory.

    • Measurements on polar liquids at a microwave frequency — evaluation of molecular parameters — a new method

      M B R Murthy B S Dyasagar R L Patil

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      A simple method of estimating the dipole moment (μ) and relaxation time (τ) of polar molecules in liquid state, from a single set of dielectric measurements at high frequency, is proposed by using the concept of dielectric virial coefficients and employing Onsager model. The proposed method is tested in a number of polar liquids and the results are discussed.

    • Temperature dependence of the fundamental band gap parameters in cadmium-rich ZnxCd1-xSe using photoluminescence spectroscopy

      Lalita Gupta S Rath S C Abbi F C Jain

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      Thin films of ternary ZnxCd1-xSe were deposited on GaAs (100) substrate using metalorganic-chemical-vapour-deposition (MOCVD) technique. Temperature dependence of the nearband-edge emission from these Cd-rich ZnxCd1-xSe (forx = 0025, 0.045) films has been studied using photoluminescence spectroscopy. Relevant parameters that describe temperature variation of the energy and broadening of the fundamental band gap have been evaluated using various models including the two-oscillator model, the Bose-Einstein model and the Varshni model. While all these models suffice to explain spectra at higher temperatures, the two-oscillator model not only explains low temperature spectra adequately but also provides additional information concerning phonon dispersion in these materials.

    • Higher-order semiclassical energy expansions for potentials with non-integer powers

      Asiri Nanayakkara

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      In this paper, we present a semiclassical eigenenergy expansion for the potential |x|α when α is a positive rational number of the form2n/m (n is a positive integer and m is an odd positive integer). Remarkably, this expansion is found to be identical to the WKB expansion obtained for the potentialxN(N-even), if2n/m is replaced byN. Taking the limitm → 2 of the above expansion, we obtain an explicit asymptotic energy expansion of symmetric odd power potentials |x|2j+1 (j- positive integer). We then show how to develop approximate semiclassical expansions for potentials |x|α when α is any positive real number.

    • Pseudo information entropy of a three-level atom interaction with two-laser fields in Λ-configuration

      A S F Obada T M El-Shahat M Abdel-Aty

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      In this report we investigate some aspects of the pseudo entropy of multi-level system in the language of quantum information theory. The influence of the non-linear interaction and detuning parameter on the properties of the pseudo information entropy is examined.

    • New isothermal equation of state of solids applied to high pressures

      Piyush Kuchhal Narsingh Dass

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      In the present paper, a new two-parameter inverted equation of state (EOS) is developed which is found to be working very well in the high-pressure region. To check its success and validity, this EOS has been applied in a number of solids. The computed volume compression is found to be in very good agreement with the experimental data in the whole range of pressure in all the solids. The minimum and the maximum pressure range used in the present study is 0–320 kbar and 0–3000 kbar, respectively.

    • Relaxation phenomena of polar non-polar liquid mixtures under low and high frequency electric field

      K Dutta S K Sit S Acharyya

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      Simultaneous calculation of the dipole moment μj and the relaxation time τj of a certain number of non-spherical rigid aliphatic polar liquid molecules (j) in non-polar solvents (i) under 9.8 GHz electric field is possible from real ε′ij and imaginary ε″ij parts of the complex relative permittivity ε*ij. The low frequency and infinite frequency permittivities ε0ij and ε∞ij measured by Purohitet al [1,2] and Srivastava and Srivastava [3] at 25, 35 and 30°C respectively are used to obtain static μs. The ratio of the individual slopes of imaginary σ″ij and real σ′ij parts of high frequency (hf) complex conductivity σ*ij with weight fractionswjatwj → 0 and the slopes of σ″ij— σ′ij curves for differentwjs [4] are employed to obtain τjs. The former method is better in comparison to the existing one as it eliminates polar-polar interaction. The hf μjs in Coulomb metre (C m) when compared with static and reported μs indicate that μs s favour the monomer formations which combine to form dimers in the hf electric field. The comparison among μs shows that a part of the molecule is rotating under X-band electric field [5]. The theoretical μtheos from available bond angles and bond moments of the substituent polar groups attached to the parent molecules differ from the measured μjs and μs to establish the possible existence of mesomeric, inductive and electromeric effects in polar liquid molecules.

    • Observation of very low frequency emissions at Indian Antarctic station, Maitri

      R P Patel R P Singh Ashok K Singh A K Gwal D Hamar

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      Recently, we have succeeded in recording VLF emissions at the Indian Antarctic station, Maitri (geom. lat. 62°S, geom. long. 57.23°E,L = 45) using a T-type antenna, pre/main amplifiers and digital audio tape recorder. VLF hiss in the frequency ranges 11–13 kHz and 13–14.5 kHz and some riser-type emissions in the frequency range 3–5 kHz and magnetospheric lines at about 6.2, 8.0 and 9.2 kHz are reported for the first time. The generation and propagation mechanism of these emissions are discussed briefly.

    • Comment: “On the computation of molecular auxiliary functions $A_{n}$ and $B_{n}$”

      Frank E Harris

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      Guseinov, Mamedov, Kara and Orbay (Pramana – J. Phys. 56, 691 (2001)) propose methods for evaluating the molecular auxiliary functions $A_{n}(p)$ and $B_{n}(pt)$ for the range $17\leq n \leq 60$ and $25 \leq pt\leq 60$. However, their procedure for $A_{n}(p)$ is not new, and that for $B_{n}(pt)$ is less efficient for their target range than another well-known method. Their approach does have merit for smaller non-zero values of $pt$. Two minor errors in table 1 of their paper are also identified.

    • Response to the Comment: “On the computation of molecular auxiliary functions $A_{n}$ and $B_{n}$”

      I I Guseinov

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      The Comment ‘on the computation of auxiliary functions $A_{n}(p)$ and $B_{n}(pt)$’ (F E Harris, Pramana – J. Phys. 61, C779 (2003)) is analysed in the arbitrary range of parameters 𝑛, 𝑝 and $pt$. It is shown that our downward recursion approach for $B_{n}(pt)$ in the range $(n/pt)> 1$ is more efficient than the well-known upward recursion method, and the upward recursion procedure for $A_{n}(p)$ does not have merit for smaller non-zero values of $p(p < 0.01)$.

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