• Volume 10, Issue 6

      June 1978,   pages  551-648

    • Upper bounds on the wave function renormalization constant of pion

      M K Parida N Giri

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      Using unitarity, analyticity and the hypothesis of Bjorken scaling inequalities have been derived for the upper bounds on the wave function renormalization constant of pion.

    • Magnetic contributions to high energy inverse bremsstrahlung process

      G Ramachandran R S Keshavamurthy

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      Magnetic contribution to inverse bremsstrahlung is estimated at high energies. It begins to dominate over the Coulomb contribution in the ratioCE22 tan2 (θ2/2) (1+sin2 (θ2/2)) whereE2 andθ2 denote the energy and angle of the accelerated electron andC is essentially a nuclear constant.

    • Static,c-number solutions of a two dimensional sine-Gordon-like field equation

      K Babu Joseph A N Muraleedhara Shenoi

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      A sine-Gordon type scalar field with a$$\cos ^4 [(\sqrt {\bar \lambda } \phi )/m]$$ potential in two dimensions is studied and a static,c-number, stable, finite energy solution obtained. The intersoliton potential is evaluated for this model and is shown to be long range, attractive and ‘strong’ in the weak coupling regime. A positronium-like spectrum of bound states of the soliton-antisoliton pair is derived using this potential. The coupling with a massless quark field is discussed and an exact, stable and analytic solution of the spinor field exhibiting confinement in one space dimension is obtained.

    • Quark charges and colour gluon mass from deep-inelastic bremsstrahlung

      P N Pandita

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      We derive sum rules for the structure functionV(x) for the ‘three-photon’ processe±+pe±+γ+X which can distinguish between various colour models below colour threshold, independently of the quark and gluon distributions. A careful study of the sum rule forV(x) in the broken colour gauge theory model can in principle be used to determine the colour gluon mass. Invoking the specific assumptions of the dominance ofp-type quarks and neglecting the sea of quark-antiquark pairs, we also obtain bounds forV(x) in terms ofvW2 (x) which can distinguish between various colour models below colour threshold.

    • An angular momentum expansion of energy and structure of high spin states

      M Satpathy R Sahu A Ansari L Satpathy

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      A new angular momentum expansion of level energies of ground-state band of even-even nuclei has been obtained which is found to converge rapidly even for the most back-bending nuclei. Attempts have been made to interpret the parameters and calculate them microscopically. It is found that nuclear structure in the forward bending region is quite different compared to that in the back-bending region.

    • X-ray determination of the mean Debye-Waller factors, amplitudes of vibration and Debye temperatures of six crystals with CsCl structure

      K G Subhadra D B Sirdeshmukh

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      From the integrated intensities of Bragg reflections measured at room temperature with an x-ray powder diffractometer, the mean Debye-Waller factorB, the average r.m.s. amplitude of vibration (ū2)1/2 and the Debye temperatureθ, have been determined for six crystals with the CsCl structure.

      The energy of formation of a Schottky pair in these crystals has been estimated from an empirical relation between the x-ray Debye temperature and the energy of formation.

    • Dislocations and their spatial configuration in amethyst crystals

      M S Joshi M A Ittyachen P N Kotru

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      Etch patterns produced on habit rhombohedral faces and rhombohedral cleavages of amethyst crystals are described and illustrated. Fidelity of etchants used is assessed. Also described are paired pits produced on match cleavages etched with the same or different etchants. By prolonged etching experiments it is established that the dislocations penetrate into the body of the crystal. Spatial distribution of dislocation in the body of the crystal is worked out. Uniformly spaced etch pits in an array observed on match cleavages (etched with different etchants) are attributed to low-angle tilt boundaries.

    • Growth and kinetic studies of lead carbonate whiskers in silica gel

      K Mohanan Pillai M A Ittyachen

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      Lead carbonate whiskers were grown by diffusion of ammonium carbonate in the silica gel charged with lead nitrate. It is found that low pH is preferred to the whisker growth. In addition to straight whiskers gently curved whiskers are also found. Curving of whiskers is found to be maximum at high concentration of carbonate ions. Growth kinetics of whiskers are studied by changing the parameters of gel growth. It is found that the parabolic relationship between dimension and growth period is obeyed in this.

    • Three impurity cluster in a diatomic linear chain

      P Nayak S N Behera

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      The modes of vibration of a three impurity cluster in a diatomic linear chain is studied. The configuration of the three impurity atoms is such that two of these go into next nearest neighbour sites in one of the sub-lattices whereas the third occupies the central in between site in the other sub-lattice. New local, gap and inband modes are seen to exist, besides the ones corresponding to the impurity pairs. A new feature which appears is that the frequencies of some of the pair modes remain totally unaffected in the presence of the third impurity atom.

    • Modulational instability of ion-acoustic-waves in two electron temperature plasmas

      A S Sharma B Buti

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      The envelope properties of ion-acoustic waves in a two-electron-temperature plasma are studied. The nonlinear Schrödinger equation describing the envelope of these waves is obtained from the plasma fluid equations by employing the Krylov-Bogoliubov-Mitropolsky perturbation method. It is shown that the ion-acoustic waves can be modulationally unstable or stable depending on the ratios of the densities and the temperatures of the hot and the cold electron components. Even a small fraction of the cold electron component can drastically affect the stability of the system.

    • Second virial coefficient for a mixture of nonspherical molecules of arbitrary symmetry

      S Singh K P Shukla

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      The mixture and interaction second virial coefficients of a binary gas mixture of nonspherical molecules of arbitrary symmetry have been calculated for a set of unlike force parameters which is obtained from the force parameters for like interactions by using empirical combination rules. In the calculation molecular anisotropy of very general type has been accounted. The relative contribution of each branch of interactions has been evaluated as a function of temperature. The theoretical values of interaction second virial coefficient have been compared with the experimental data of N2+A, N2+He, N2+H2, N2+O2, N2+C2H4, N2+C2H6, CO2+A, CO2+H2, CO2+N2, CO2+O2, CO2+CO, CO2+C2H4, CO2+C2H6, O2+A and H2+CO. The agreement between theory and experiment is satisfactory for all the systems. Numerical estimations of the mixture second virial coefficients as a function of temperature and composition are given for the systems CO2+A, CO2+H2, CO2+N2, CO2+O2 and CO2+CO.

    • On the symmetries between neutrino and antineutrino-nucleon elastic scattering

      M T Teli R G Takwale

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