• Volume 24, Issue 4

      April 1985,   pages  1-655

    • Triangle anomaly free weak interaction with two neutral currents

      C V A V B Chandra Raju

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      Considering that the neutral interaction is free of triangle anomalies we derive an expression for the most general neutral interaction with two neutral currents. We show that the Bargers version is a special case. We also determine the interaction wheneverZ, D are mass eigen states and show that this differs from the Barger’s version in an essential way.

    • Laser Raman spectroscopic study of ferroelastic LiCsSO4

      B Raghunatha Chary H L Bhat P Chandrasekhar P S Narayanan

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      Lithium caesium sulphate has been reported to undergo a phase transition from the room temperature orthorhombic phase with space groupP cmn to a final phase with space groupP 22/n. Though a sharp anomaly in its physical properties has been found at 202.0;K, it was found that there was a need for careful investigations in the vicinity of 240 and 210.0;K. Since the changes in the crystal structure involve primarily a rotation of the SO4 tetrahedron about thec-axis and as this may be reflected both in the intensity and polarisation of the internal as well as external phonon modes, the laser Raman spectra of oriented single crystals of LiCsSO4 at different temperatures were investigated. For correlation and definite identification of the spectral features, its infrared absorption spectrum was also studied. An analysis of the intensities and polarizations of the internal modes of the sulphate ions reveals the change in symmetry of the crystal. The integrated intensity and peak height of thev1 line, plotted against temperature show anomalous peaks in the region of the phase transition. Differential scanning calorimetric study gives the enthalpy change ΔH across the phase transition to be 0.213 kJ/mol.

    • Dynamical scaling for spin waves in dilute ferromagnets

      Deepak Kumar

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      The ambiguity in the application of the principle of dynamic scaling to spin waves in dilute ferromagnets is resolved by taking account of the fractal nature of the infinite percolation cluster.

    • A mean-field, effective medium theory of random binary alloys IV. The Heisenberg model with competing interactions and the mixed phase

      A Mookerjee S B Roy

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      The Heisenberg model with competing interactions is studied within a mean field, effective medium approach. The phase diagram indicates the existence of a mixed or randomly canted phase just beyond the spin glass regime. Experimental evidence of such a phase in alloys like FeCr is studied.

    • ac anddc electroluminescence in CaS:Cu, Sm phosphors

      S Bhushan F S Chandra

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      Theac anddc electroluminescence in CaS:Cu, Sm have been investigated. The luminescence spectra show three peaks in the visible region. The brightness-voltage dependence satisfies the relationB=B0 exp (−b/V1/2) with two modes of variation. The nature of this dependence indc andac at different frequencies is discussed. The electroluminescence brightness also depends on the temperature of the phosphors and shows a peak around 80.0;C. The electroluminescence efficiency increases with applied voltage up to 2200 V and this dependence on V is explained on the basis of a transport process of the Schottky emission type.

    • Two-mode para-Bose number states

      G M Saxena C L Mehta

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      Two-mode para-Bose number states are discussed. The two-mode system has been chosen as it is a representative of the multi-mode system. Salient properties like normalization, orthogonality and degeneracy of these states have also been discussed.

    • Coherent states of a damped harmonic oscillator

      S K Bose U B Dubey V N Tewari

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      We construct here the coherent states (annihilation operator eigenstates) of a damped harmonic oscillator. These coherent states, which are normalizable, have the desired behaviour in the classical limit (ℏ→0).

    • Schwinger’s action principle, supersymmetry and path integrals

      S P Misra Tapaswini Pattnaik

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      We use Schwinger’s action principle in quantum mechanics to obtain the quantisation from Lagrangian for the fermionic variables, as well as when it contains auxiliary coordinates. We illustrate this with a supersymmetric Lagrangian which naturally includes auxiliary variables. We further show that the action principle also leads to Feynman’s path integral quantisation, which is aesthetically pleasing.

    • Electroluminescence and N2 laser excited fluorescence of high field electroformed castor oil and liquid paraffin

      S M Pillai C P G Vallabhan

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      The method of preparation of electroluminescent (el) cells using dielectric liquids like castor oil and liquid paraffin by an electroforming process is presented. Theel spectrum of the material derived from castor oil exhibits a large number of sharp lines which can be grouped into four distinct series superposed on a broad background. Theel spectrum of liquid paraffin cells does not show any significant line features. The N2 laser excited fluorescence spectra of these oils and of the respective electroformed materials are also recorded. The electrical and brightness characteristics of these cells are discussed in detail.

    • Fractionally charged non-leaking dyons and fermions in a bag

      S M Roy Virendra Singh

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      We consider a fermion of chargee confined to a spherical bag with a Dirac monopole of strengthg at its centre. We find that the boundary conditions making the lowest angular momentum hamiltonian self-adjoint are characterized by a unitary matrixU, and the corresponding vacuum charge has a fractional part 2|eg|α/π where detU = -exp (2). Boundary conditions for conservation of helicity,CP, CT andPT are displayed. We demonstrate the possibility of a fractionally charged dyon whose interaction with a fermion conserves helicity. We also show thatthe simultaneous validity of helicity, CP, CT and PT requires integer vacuum charge.

    • Ground state baryon magnetic moments and nucleon axial vector coupling

      Pashupati N Pandit M P Khanna

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      Ground-state baryon magnetic moments and nucleon axial vector coupling are calculated usingqcd inspired configuration mixing and relativistic corrections. Unlike earlier attempts, we incorporate a natural mass scale for quarks, taken as one third the nucleon mass for up and down quarks, and the strange quark mass suggested by the Lipkin’s sum rule. In the parameter-free non-relativistic limit, we find a fairly good fit, which improves upon including relativistic corrections.

    • 51(p, n)51Cr reaction from Ep 1.9 to 4.5 MeV

      S Kailas S K Gupta S S Kerekatte C V Fernandes

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      The total cross-section for the reaction51V(p, n)51Cr has been measured fromEp 1.9 to 4.5 MeV by using two different techniques: (i) by detecting the neutron using the 4π neutron counter and (ii) by measuring the activity of the residual nucleus51Cr. The two measurements are consistent with each other and together they are in good agreement with the data of Zyskindet al. The thermonuclear reaction rates have also been extracted starting from these cross-sections.

    • Pre-equilibrium emission effect in (n, p) reaction cross-sections at 14.8 MeV

      J P Gupta H D Bhardwaj R Prasad

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      The influence of pre-equilibrium emission on (n, p) reaction cross-sections at 14.8 MeV has been studied. Cross-sections for (n, p) reactions have been measured by the activation technique at 14.8 .1; 0.5 MeV neutron energy. The experimental cross-section values have been compared with the calculated values at 14.8 MeV with and without considering the pre-equilibrium emission. Equilibrium calculations have been performed according to the statistical model of Hauser and Feshbach while the hybrid model has been used to include the pre-equilibrium contribution. Pre-equilibrium emission has been considered only in the first emission step. The comparison of experimental and calculated values clearly indicates the presence of pre-equilibrium emission.

    • A quasi random search technique for functional fitting of detector responses

      Tapas Bandyopadhyay P K Sarkar

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      The problem of nonlinear optimization is encountered while fitting the observed response of certain radiation detectors. In this paper the development of an optimizing technique based on quasi random search is described. The performance of this technique is compared with other existing methods of gradient search and linear Taylor differential correction technique in the case of fitting the photopeak responses of Nal(Tl) detectors. Our results are favourable especially when the observed data are associated with poor statistics.

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