• Volume 46, Issue 5

      May 1996,   pages  315-387

    • Geometric phasea la Pancharatnam

      Veer Chand Rakhecha Apoorva G Wagh

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      In mid-1950s, Pancharatnam [1] encountered the geometric phase associated with the evolution along a geodesic triangle on the Poincaré sphere. We generalize his 3-vertex phase and employ it as the fundamental building block, to geometrically construct a general ray-space expression for geometric phase. In terms of a reference ray used to specify geometric phase, we delineate clear geometric meanings for gauge transformations and gauge freedom, which are generally regarded as mere mathematical abstractions.

    • Time dependent canonical perturbation theory III: Application to a system with nonconstant unperturbed frequencies

      Mitaxi P Mehta B R Sitaram

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      In this communication, we report the results of the application of time dependent perturbation theory to a non-integrable Hamiltonian which is a perturbation on a Hamiltonian with nonconstant frequencies. The theory provides good time dependent local constants of motion and also gives good approximation for mapping of solutions for a time limit determined by the nearest singularity in complexε plane for fixed real time and the order of calculation.

    • Cosmic strings in Bianchi II, VIII and IX spacetimes: Integrable cases

      L K Patel S D Maharaj P G L Leach

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      We investigate the integrability of cosmic strings in Bianchi II, VIII and IX space-times using a Lie symmetry analysis. The behaviour of the gravitational field is governed by solutions of a single second order nonlinear differential equation. We demonstrate that this equation is integrable and admits an infinite family of physically reasonable solutions. Particular solutions obtained by other authors are shown to be special cases of our class of solutions.

    • A spherically symmetric gravitational collapse-field with radiation

      P C Vaidya L K Patel

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      An interior spherically symmetric solution of Einstein’s field equations corresponding to perfect fluid plus a flowing radiation-field is presented. The physical 3-spacet=constant of our solution is spheroidal. Vaidya’s pure radiation field is taken as the exterior solution. The inward motion of the collapsing boundary surface follows from the equations of fit. An approximation procedure is used to get a generalization of the standard Oppenheimer-Snyder model of collapse with outflow of radiation. One such explicit solution has been given correct to second power of eccentricity of the spheroidal 3-space.

    • Static and dynamic properties of heavy light mesons in infinite mass limit

      D K Choudhury Pratibha Das

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      We summarize the consequences of the infinite limit of heavy quark mass in the results of form factors, charge radii and decay constants of heavy light mesons within a QCD inspired quark model recently reported.

    • Effective potentials and threshold anomaly

      SVS Sastry S K Kataria

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      The strongE andL dependence of the effective elastic channel potentials is shown to be an implicit radial kinetic energy (ε) dependence. It is also shown that this effective potential satisfies the dispersion relation inε variable at the strong absorption radius. Further, the experimental data for both elastic and fusion channels are consistent with thisL-dependence of the corresponding effective potentials. The effective transfer channel potentials derived using CRC code FRESCO are shown to exhibit strong energy dependence as a result of couplings. The energy dependence of effective transfer strength for16O+208Pb and16O+232Th systems is determined using the experimental transfer angular distributions.

    • Depopulation of Na(8s) colliding with ground state He: Study of collision dynamics

      A A Khan K K Prasad S K Verma V Kumar A Kumar

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      A systematic study of the collison dynamics associated with depopulation of Na(8s) atom colliding with ground state He has been made by applying the semi-classical impact parameter method using molecular orbital (MO) basis sets of different sizes. The cross-sections for total depopulation of the parent atom as well as those for individual transitions have been calculated. It is shown that the basis set must be large enough so as to include not only the immediate adjacent states coupling with the parent state but also other nearby states, which can affect the overall flux distribution in the reaction.

    • Multiconfiguration Hartree-Fock calculations in Cr5+, Mn6+ and Fe7+

      S N Tiwary P Kumary R P Roy

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      The multiconfiguration Hartree-Fock (MCHF) method is used to calculate the excitation energies and oscillator strengths, of both the length (fL) and velocity (fV) forms, for 1s22s22p63s23p63d2D→1s22s22p63s23p53d22P0,2D0,2F0 transitions in Cr5+, Mn6+ and Fe7+ ions of the potassium isoelectronic sequence. Comparison is made with our earlier relevant results obtained by employing the configuration interaction (CI) method which is closely related to the MCHF method. Our present investigation demonstrates that the MCHF method is more accurate than the CI method in all ions of present consideration.

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