• Volume 20, Issue 5

      May 1983,   pages  363-438

    • Study of isotope shifts, isotone shifts and nuclear compressibility from the analysis of muonic x-ray transitions

      K V Subba Rao A A Kamal

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      Muonic x-ray transitions in various spherical nuclei in the region 13⩽Z⩽83 have been analysed and the isotope and isotone shifts in charge radiusR are investigated. AssumingR=r0A1/3, the isotopic and isotonic behaviour of the parameterr0 (=RA−1/3) is also studied. The variation ofr0 with mass numberA reveals the variation of average nucleon density, which in turn sheds light on the compressibility of nuclear matter. The isotope and isotone shifts inR exhibit the shell effects in the vicinity of magic neutron and proton numbers: 20, 28, 50, 82 and 126. The results indicate that neutron-proton interaction is maximum at the beginning of a major neutron shell and decreases gradually as the shell gets filled up. The behaviour of parameterr0 clearly suggests that low-Z nuclei are highly compressible while high-Z nuclei are more or less incompressible. The parameterr0 too is observed to exhibit profound shell effects.

    • Local charge compensation in the quark-cascade jet-production model

      S P Misra B K Parida

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      The charge correlations and the local charge compensation mechanism in rapidity space for quark jets are analysed in the framework of the quark-cascade jet-production model. The calculated results are compared with those observed experimentally in antineutrino-nucleon processes, and for the short range charge correlations observed ine+e annihilation experiments. The results appear consistent with the quark-cascade model.

    • Quadrupole interaction of tantalum impurities in bismuth metal

      S N A Jaaffrey J Varma

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      The time differential perturbed angular correlation technique has been used in the measurement of the electric quadrupole interaction of Ta impuritiy in bismuth metal. The interaction frequencies at 293, 400 and 500 K have been observed to be 288±1.5, 266.9±3 and 244.5±4.3 MHz respectively. The electric field gradient at 293 K is 4.75±0.3 × 1017 V/cm2 with the temperature coefficientB=2.2±0.2 × 10−5 (K)−3/2.

    • Charge imbalance due to thermoelectric effects in superconductors: A two fluid description

      B A Mattoo Y Singh

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      Using a generalised two-fluid picture for the charge of a superconductor, the generation of charge imbalance by a temperature gradient under different conditions is studied. The voltage developed by a temperature gradient in the presence of supercurrent is estimated. The results agree with experiment. The results obtained for the generation of charge imbalance in the absence of imposed current agree with those obtained using other techniques.

    • Density expansion of viscosity coefficient

      A K Heblekar

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      The formalism developed earlier has been extended to obtain the density expansion of viscosity coefficient. The important role played by the Hartree average energy in obtaining an explicit temperature dependence for the density coefficients of the viscosity is demonstrated. The results obtained are compared with the available experimental data for the first density coefficient. A satisfactory agreement between theory and experiment is found.

    • Solitons in a linear lattice with defects

      V Narasimha Iyer K S Viswanathan

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      Solitons are generated in an anharmonic linear lattice in which neighbouring atoms interact through a Morse potential by giving either a strong initial impulse or a large displacement to an end atom. Studies on the variation of the characteristic properties of the soliton with the strength of the initial pulse show that the velocity and the amplitude of the soliton increase with the strength of the initial impulse, but below a certain critical value for the initial impulse, only an oscillatory tail is generated. It is shown that when a defect is present in the lattice, a localised mode appears at the site of the defect and additional solitons travelling forward or even backwards, are generated. When two solitons collide at a defect region, they reemerge but leave a localised mode at the site of the defect. If an initial velocity is imparted to a particular particle, synchronously with the crossing of the particle by the soliton, a localised mode emerges at the site of the particle and additional solitons are also generated. When a soliton moves from a denser to a rarer medium, a strong localised pulse is created near the region of the density discontinuity and additional solitons appear; and further a weak oscillatory tail is left behind in the denser medium. On the other hand, if a soliton moves from a rarer to a denser medium, it is reflected back and a small localised mode is generated at the site of the density discontinuity. The variation of amplitude of the soliton with the velocity of propagation is also studied.

    • Soliton-like solutions of some nonlinear theories and transformations among them

      G P Malik J Subba Rao Gautam Johri

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      The observation that the soliton-like solutions of a given second-order nonlinear differential equation define the separatrix of the equivalent autonomous system is used to obtain the one-soliton solutions for theφ4 theories (the usual and the one with the wrong sign of the mass term), theφ6, theφ8, the sine-Gordon theories and the KdV equation. Transformations are given which transform the sine-Gordon equation into an equation belonging to theφ2n class of theories. A procedure is evolved for obtaining the two-soliton solutions for the sine-Gordon theory without the use of Backlund transformations; it is suggested that this procedure may be useful for investigating the existence of similar solutions for theories of the polynomial type.

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