• Volume 44, Issue 2

      February 1995,   pages  85-200

    • A new computation scheme for triangular quantum billiards

      Paolo Bellomo

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      A new scheme for computing the eigenvalues and eigenstates of the Laplacian with Dirichlet boundary conditions on arbitrary triangular domains is presented. Its reliability is tested by comparing numerical results with analytical ones whenever possible. The computation of eigenvalues shows a good agreement with analytical results. The procedure is shown to give accurate results also in the case of eigenfunctions computation. Finally, the sensitivity of our scheme to the geometry of the domain is discussed and the algorithm is shown to detect small changes in the shape of the domain.

    • On the accuracy of wavefunctions obtained by the Fourier grid Hamiltonian method

      P Dutta S P Bhattacharyya

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      The quality of wavefunctions obtained by the Fourier grid Hamiltonian (FGH) method is analyzed. The criteria used for judging the quality are the extent to which virial, hypervirial and Hellmann-Feynman theorems are satisfied by the numerically computed FGH-wavefunction. The quality of the FGH-wavefunction is also examined from the point of view of local error in the wavefunction. It is shown that high quality wavefunctions can be obtained from the FGH recipe if the grid length (L) and grid spacings are chosen after properly examining the range of the potential and its nature.

    • Conversion of a chaotic attractor into a strange nonchaotic attractor in an one dimensional map and BVP oscillator

      S Rajasekar

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      In this paper we investigate numerically the possibility of conversion of a chaotic attractor into a nonchaotic but strange attractor in both a discrete system (an one dimensional map) and in a continuous dynamical system — Bonhoeffer—van der Pol oscillator. In these systems we show suppression of chaotic property, namely, the sensitive dependence on initial states, by adding appropriate i) chaotic signal and ii) Gaussian white noise. The controlled orbit is found to be strange but nonchaotic with largest Lyapunov exponent negative and noninteger correlation dimension. Return map and power spectrum are also used to characterize the strange nonchaotic attractor.

    • Wormholes in higher dimensions with Gauss-Bonnet terms

      B C Paul A Beesham S Mukherjee

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      A class of wormhole solutions permitted in a theory with Gauss-Bonnet terms in the gravitational action in higher dimensions have been studied. The case of de-Sitter type instantons, with a compact inner space, are of particular interest here. Some of the configurations, when continued analytically to the Lorentzian metric lead to the standard inflationary universe. Some multiple-sphere configurations of the type studied by Myers have also been noted. The Euclidean action for the solutions has been calculated and the relevance of the solutions in the quantum creation of the universe has been considered.

    • Magnetic moments of decuplet baryons in an independent particle potential model

      N Barik P Das A R Panda

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      Magnetic moments of decuplet baryons have been calculated in a relativistic independent quark model with a phenomenological potential in equally mixed scalar-vector harmonic form. Such a model has been successful in describing wide ranging hadronic phenomena in mesonic and baryonic sectors. Using the solutions of the constituent quark orbitals with the model parameters taken from its earlier applications, the magnetic moments of decuplet baryons Δ++ and Ω have been obtained which are in good agreement with the available experimental data. However, the agreement is found to be much better when the magnetic moment ratios such as μδ++/μp and μΩ-/μΛ are considered. Model predictions for the magnetic moments of other decuplet baryons together with the charge radii have also been calculated which may be verified in future experiments.

    • A new approach for heavy ion fusion spin distribution

      S V S Sastry A K Mohanty S K Kataria

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      The method of optical model analysis of generalized elastic scattering angular distributions (GESA) has been applied to heavy ion scattering to derive fusion spin distributions. This method is used to reproduce the coupled channel fusion spin distributions. When applied to experimental data, particularly to the fissile systems like16O +232Th, the method gives large mean square spin values in agreement with “anomalous” values derived from experimental fission fragment anisotropies.

    • Momentum- and energy-dependence ofJ/Ψ suppression in relativistic heavy ion collisions

      R S Kaushal S K Karn

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      With a view to understand the available data on the momentum- and energy-dependences of theJ/Ψ suppression, we compute the suppression rate within the framework of a hydrodynamical evolution model for the quark-gluon plasma (QGP) formation. We make use of an ansatz for the temperature profile function which accounts not only for the space and time evolutions of QGP but also for the possibility of a mixed phase in the boundary region of the deconfined phase. While the predictions are made for the longitudinal momentum- and energy-dependences of the suppression rate, a satisfactory agreement with the available data is found for its dependences on the transverse momentum and the transverse energy.

    • Deep inelastic collisions of32S +27Al reaction at 130 MeV bombarding energy

      R K Choudhury D M Nadkarni V S Ambekar B V Dinesh A Saxena M S Samant D C Biswas L M Pant

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      The32S +27Al reaction was studied to investigate the deep inelastic collisions at a bombarding energy of 130 MeV which is well above the Coulomb barrier. The energy distributions of the binary decay products of 6⩽Z⩽10 were determined using a large area position sensitive ionization chamber. The average kinetic energies of the reaction products indicate that the exit shapes correspond to highly stretched scission configurations in the deep-inelastic processes.

    • Trinucleon system with Reid soft core potential by hyperspherical harmonics expansion method

      Satadal Bhattacharyya Tapan Das Kumar

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      The hyperspherical harmonics expansion method has been used to solve the trinucleon system where the nucleons interact through Reid soft core potential. The binding energy of triton, both for extreme adiabatic approximation and uncoupled adiabatic approximation, and theS-state,S′-state andD-state probabilities are calculated and compared with the results by the Faddeev method.

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