• Volume 33, Issue 3

      September 1989,   pages  345-447

    • Announcement

      G Srinivasan

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    • Bivariate averaging and the Wigner distribution function

      A K Rajagopal S Teitler

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      In order to gain insight into the nature of the Wigner and related distribution functions, bivariate averaging functions of real unbounded variables with absolutely continuous marginals that are ordinary probabilities are considered. Accordingly variables are chosen to be phase space variables that are respectively eigenvalues of position and momentum operators. The impact of the condition that the marginals are squared magnitudes of amplitudes that are Fourier transforms of one another is emphasized by the delay of the introduction of this Fourier transform condition until after the form for a bivariate distribution with the given marginals is obtained. When the respective amplitudes are fourier transforms of one another, special cases of the bivariate averaging function correspond to generalized Wigner functions characterized by a parameterα. Such anα-Wigner function can be used as the basis of a consistent averaging procedure if an appropriate corresponding representation for underlying operators to be averaged is specified. Properties of theα-Wigner functions are summarized.

    • An improved approximate solution of Altarelli-Parisi equations

      D K Choudhury A Saikia

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      We have presented here an improved solution to Altarelli-Parisi equations, and it is found to be in good agreement with SLAC-MIT data up tox⩾0.1.

    • Giant resonances in90Zr and116Sn

      S Kailas A Saxena P P Singh Q Chen D L Friesel P Schwandt E J Stephenson

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      The giant resonance region in90Zr and116Sn excited by 270 MeV helions has been measured up to about 35 MeV excitation energy. The low and the high energy octupole resonances are seen prominently in addition to the quadrupole and the monopole resonances. The angular distribution data for the various multipoles are satisfactorily explained by the collective model calculations. The percentatge energy weighted sum rule strengths have been determined for all the prominent resonances.

    • Phase-function method for velocity-dependent potentials

      G C Sett B Talukdar

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      We have adapted the phase-function method for studying on- and off-shell properties of velocity-dependent potentials. The main result presented in this paper is an ansatz for the interpolatingT-matrix function (on- or off- the energy-shell as the case may). Based on this ansatz we have presented an efficient method for computing the off-shell extension function which plays a role in the theories of three particle system. We have demonstrated this by means of a model calculation.

    • Overtone spectra of styrene and polystyrene in the visible and near infrared regions

      T M Abdul Rasheed K P B Moosad V P N Nampoori K Sathianandan

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      Vibrational overtone spectra of styrene (liquid) and polystyrene (solid), studied by the laser-induced thermal lens (for ΔV=6) and the conventional near infrared absorption (for ΔV=3–5) techniques, are reported. For polystyrene, the overtone energy-bond length correlation predicts that the aryl CH bonds are ∼0.0005 Å longer than that in benzene, while no such conclusions could be drawn on styrene. Thesp3 CH overtones in polystyrene are observed on the low energy side of the aryl CH overtones.

    • Ignition and increase in Pease limit on current in an ohmically heated high densityZ-pinch

      A Shyam V Chitra M Srinivasan

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      Energetics of an ohmically heated deuterium-tritium high densityZ-pinch has been computed taking into account the energy deposited by the alpha particles produced by fusion. As a result, at higher plasma densities (>1027/m3) and temperatures (>4keV), the pinch current can cross Pease limit and the plasma can get ignited, yielding higher energy gain and neutron yield in a shorter confinement time.

    • Non-periodic tilings in 2-dimensions with 4, 6, 8, 10 and 12-fold symmetries

      V Sasisekharan S Baranidharan V S K Balagurusamy A Srinivasan E S R Gopal

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      The two dimensional plane can be filled with rhombuses, so as to generate non-periodic tilings with 4, 6, 8, 10 and 12-fold symmetries. Some representative tilings constructed using the rule of inflation are shown. The numerically computed diffraction patterns for the corresponding tilings are also shown to facilitate a comparison with possible X-ray or electron diffraction pictures.

    • Synergism in electron gas in crossed fields. II degenerate 3DEG—hall conductance

      R Pratap J Sreekumar

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      A microscopic many body correlation dynamics has been worked out for a 3DEG in degenerate state far removed from equilibrium, placed in crossed electric and magnetic fields of arbitrary strength. It is shown that linear electric field case gives only σ12, even though the response function retains all the nonlinear effects in the system. The nonanalytic behaviour of the response function is explicitly shown. The quantisation of Hall current comes out as a direct consequence both for odd and even filling factors, and this is due to an exact evaluation of the dynamics in the self consistent field case. Radiated energy for this system is also calculated. A comparison of the present results with those obtained based on Kubo formalism has brought out the incompatability of using external fields as ordering parameters in any expansion scheme. A further new result is the nonanalytic property of the response function obtained in the present formulation.

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