• Volume 15, Issue 6

      December 1980,   pages  507-587

    • On the normal vibrations of nonrigid molecule B(CH3)3

      T S G Krishna Murty L S R K Prasad M Kondala Rao

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      Treating the symmetry operations as transformations in higher dimensional space, it is shown that Wigner’s method can be straightaway extended to study the vibrations of nonrigid molecules exhibiting free or nearly free internal rotations. The molecule B(CH3)3 is illustrated.

    • Thermal depolarisation current study of electron irradiated fluorinated ethylene propylene

      S J Walzade J P Jog S V Bhoraskar

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      Thermally stimulated current (TSC) studies have been reported in the co-polymer of tetrafluoro ethylene and hexafluoropropylene films. Depolarisation current peaks are obtained atα1,α2 andβ relaxation temperatures of the polymer and the detrapping process is explained on the basis of its molecular motion. A cross-over electron energy of 18 keV is observed where the nature of TSC spectra undergoes a remarkable change. This is explained in relation to the surface states in FEP. Five groups of trapping levels, 0.25±0.08, 0.57±0.10, 1.07±0.1, 1.3±0.25 and 2.3±0.4 eV are obtained.

    • Fake double layers in double plasma devices

      S K Mattoo Y C Saxena A N Sekar

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      The double layer like potential jumps have been observed in a double plasma device. They do not correspond to a switching of plasma potential from one metastable state to another but are caused by the ionisation of a very minute amount of the gas that inevitably leaks into the system during the probe movement.

    • An alternative definition of the electron propagator in the superoperator form and its relation to linear response theory in a coupled-cluster framework

      M Durga Prasad Sourav Pal D Mukherjee

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      In this paper it is shown that (i) there exists an alternative definition of the superoperator resolvent for calculation of difference energy satisfying linked cluster theorem for a coupled-cluster choice of the ground-state function which may even be approximate; (ii) the pole-structure of this propagator-like function in superoperator form is shown to contain information similar to that contained in the conventional propagator. (iii) It is demonstrated that suitable “Killer conditions” and completeness of the “operator manifold”—essential for understanding the pole-structure of the propagator—can be established both for an exact and an approximate ground state function in a coupled-cluster form. (iv) It is also demonstrated that difference energies calculated with these propagator-like functions are identical to those obtained from a linear response theory in a coupled-cluster form put forward recently by Mukherjeeet al and Monkhorst.

    • On the connectivity index for lattices of nonintegral dimensionality

      Deepak Dhar

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      We define the connectivity indexc for an infinite graph by the requirement that to disconnect a subset of at leastV points from the rest of the graph requires the deletion of a minimum ofS(V) bonds whereS(V) ∼V(c−1)/c for largeV. For ad-dimensional hypercubical lattice withd integral,c=d. We construct explicit examples of lattices with nonintegral connectivity indexc, 1<c<∞. It is argued that the connectivity index is an important parameter determining the critical behaviour of Hamiltonians on these lattices.

    • Collective modes in the generator coordinate method

      P Rameshan S C K Nair

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      Using the harmonic version of the generator coordinate method, and Skyrme interaction, the frequencies of the isoscalar breathing and quadrupole modes are related to the relevant incompressibility coefficients. The possibility of extending this to spin modes is also examined. It is found that a spin incompressibility coefficient is negative for a particular set of Skyrme parameter for4He. Other sets produce low positive values and these in turn could imply a relatively low lyingS=2,T=1 state. The replacement of the three-body term by the density-dependent one, suggested by Chang provides a cure for this pathology.

    • Variation of average charged particle multiplicity inp-nucleus interactions with energy and the two component description of particle production at high energies

      G L Kaul S K Badyal I K Daftari V K Gupta B Kour L K Mangotra Y Prakash N K Rao S K Sharma Gian Singh

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      Experimental data on average shower particle multiplicity (〈Ns〉) accumulated onp-nucleus interactions in the wide momentum region of 7.1–8000 GeV/c is investigated. It is observed that 〈Ns〉 is represented exceedingly well as a function of (vvS). There are two physical processes which represent the experimental data reasonably well in the two momentum regionsviz 7.1–67.9 GeV/c and 67.9–8000 GeV/c. 〈Ns〉=a(vS)/a+b fits the data in the low momentum region, whereas 〈Ns〉=a +b ln (vvS) fits the experimental data in the high momentum region. The two physical processes are unified and represented by a single equation which is shown to be the consequence of two component theory and collective models.

    • Possible realisation and generalisation of two specific 2×2 forms

      S K Soni

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      For each of a couple of two-dimensional forms for quark mass matrix, it is discussed how that form may be realised in a certain gauge scheme (one of them in the standard model and the other in a scheme based on simple rank two times U(1)) by imposing suitable discrete symmetries and how under a certain small angle approximation that form may be regarded as the simplest member of a family of higher dimensionality forms.

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