• Volume 66, Issue 6

      June 2006,   pages  961-1151

    • Painlevé test for integrability and exact solutions for the field equations for Charap’s chiral invariant model of the pion dynamics

      Susanto Chakraborty Pranab Krishna Chanda

      More Details Abstract Fulltext PDF

      It has been shown that the field equations for Charap’s chiral invariant model of the pion dynamics pass the Painlevé test for complete integrability in the sense of Weisset al. The truncation procedure of the same analysis leads to auto-Backlund transformation between two pairs of solutions. With the help of this transformation non-trivial exact solutions have been rediscovered

    • On a revisit to the Painlevé test for integrability and exact solutions for Yang’s self-dual equations forSU (2) gauge fields

      Susanto Chakraborty Pranab Krishna Chanda

      More Details Abstract Fulltext PDF

      Painlevé test (Jimboet al [1]) for integrability for the Yang’s self-dual equations forSU(2) gauge fields has been revisited. Jimboet al analysed the complex form of the equations with a rather restricted form of singularity manifold. They did not discuss exact solutions in that context. Here the analysis has been done starting from the real form of the same equations and keeping the singularity manifold completely general in nature. It has been found that the equations, in real form, pass the Painlevé test for integrability. The truncation procedure of the same analysis leads to non-trivial exact solutions obtained previously and auto-Backlund transformation between two pairs of those solutions

    • Effect of entrance channel parameters on the fusion of two heavy ions: Excitation functions of reaction products in16O +66Zn and37Cl +45Sc reactions

      Suparna Sodaye B S Tomar A Goswami

      More Details Abstract Fulltext PDF

      Excitation functions of reaction products formed in16O +66Zn and37Cl +45Sc systems, leading to the same compound nucleus,82Sr, were measured using recoil-catcher technique and off-line γ-ray spectrometry. The contribution of non-compound processes like transfer and incomplete fusion (ICF) reactions to the cross-sections of different evaporation residues were delineated by comparing the experimental data with the predictions of Monte Carlo simulation code PACE2. The results show that non-compound processes become a significant fraction of the total reaction cross-section in16O +66 systems in the beam energy range studied, while37Cl +45Sc gives mainly compound nucleus products. The mass asymmetry dependence of the fusion and non-compound cross-sections have been analysed in terms of the static fusion model and sum rule model

    • Dependence of adiabatic population transfer on pulse profile

      S Dasgupta T Kushwaha D Goswami

      More Details Abstract Fulltext PDF

      Control of population transfer by rapid adiabatic passage has been an established technique wherein the exact amplitude profile of the shaped pulse is considered to be insignificant. We study the effect of ultrafast shaped pulses for two-level systems, by density-matrix approach. However, we find that adiabaticity depends simultaneously on pulse profile as well as the frequency modulation under non-resonant conditions

    • Excited states of muonium in atomic hydrogen

      V S Kulhar

      More Details Abstract Fulltext PDF

      Muonium formation in excited states in muon-hydrogen charge-exchange collision is investigated using a method developed in a previous paper. Differential cross-section results are found to resemble positronium formation cross-section results of positron—hydrogen charge-exchange problem. Forward differential and integrated cross-sections are computed for muon energy of 2 keV and higher. Total muonium formation cross-sections are computed using Jackson and Schiff scaling rules. Muonium formation cross-section results obtained from proton—hydrogen charge-exchange cross-section results, using velocity scaling are compared with the results of the present calculation

    • High sensitivity probe absorption technique for time-of-flight measurements on cold atoms

      A K Mohapatra C S Unnikrishnan

      More Details Abstract Fulltext PDF

      We report on a phase-sensitive probe absorption technique with high sensitivity, capable of detecting a few hundred ultra-cold atoms in flight in an observation time of a few milliseconds. The large signal-to-noise ratio achieved is sufficient for reliable measurements on low intensity beams of cold atoms. We demonstrate the high sensitivity and figure of merit of the simple method by measuring the time-of-flight of atoms moving upwards from a magneto-optical trap released in the gravitational field

    • Computation of the lateral and axial point spread functions in confocal imaging systems using binary amplitude mask

      A M Hamed

      More Details Abstract Fulltext PDF

      In this paper, a novel aperture based on Tolardo concept composed of a central clear disc surrounded by a series of black and white (B/W) concentric annuli of equal transmittance is presented. Different apodized apertures of different number of B/W annuli are suggested in order to improve further the three-dimensional resolving power of confocal imaging systems. Both the axial and lateral point spread functions (PSF) and the corresponding irradiances are computed in both cases of conventional and confocal scanning microscopes for the above-mentioned amplitude filters. These results of axial and lateral irradiances are graphically represented by constructing a computer program using MATLAB. The obtained results are compared with that obtained in case of circular, annular, and Martinez-Corral apodized aperture

    • Ion-acoustic solitons in multispecies spatially inhomogeneous plasmas

      Tarsem Singh Gill Harvinder Kaur Nareshpal Singh Saini

      More Details Abstract Fulltext PDF

      Ion-acoustic solitons are investigated in the spatially inhomogeneous plasma having electrons-positrons and ions. The soliton characteristics are described by Korteweg-de Vries equation which has an additional term. The density and temperature of different species play an important role for the amplitude and width of the solitons. Numerical calculations show only the possibility of compressive solitons. Further, analytical results predict that the peak amplitude of soliton decreases with the decrease of density gradient. Soliton characteristics like peak amplitude and width are substantially different from those based on KdV theory for homogeneous plasmas

    • Application of maximum entropy method for the study of electron density distribution in SrS, BaS and PuS using powder X-ray data

      R Saravanan

      More Details Abstract Fulltext PDF

      A study of the electronic structure of the three sulphides, SrS, BaS and PuS has been carried out in this work, using the powder X-ray intensity data from JCPDS powder diffraction data base. The statistical approach, MEM (maximum entropy method) is used for the analysis of the data for the electron density distribution in these materials and an attempt has been made to understand the bonding between the metal atom and the sulphur atom. The mid-bond electron density is found to be maximum for PuS among these three sulphides, being 0.584 e/Å3 at 2.397 Å. SrS is found to have the lowest electron density at the mid-bond (0.003 e/Å3) at 2.118 Å from the origin leaving it more ionic than the other two sulphides studied in this work. The two-dimensional electron density maps on (100) and (110) planes and the one-dimensional profiles along the bonding direction [111] are used for these analyses. The overall and individual Debye-Waller factors of atoms in these systems have also been studied and analyzed. The refinements of the observed X-ray data were carried out using standard softwares and also a routine written by the author

    • Damage spreading on the 3–12 lattice with competing Glauber and Kawasaki dynamics

      Z Z Guo Xiao-Wei Wu Chun-An Wang

      More Details Abstract Fulltext PDF

      The damage spreading of the Ising model on the 3–12 lattice with competing Glauber and Kawasaki dynamics is studied. The difference between the two kinds of nearest-neighboring spin interactions (interaction between two 12-gons, or interaction between a 12-gon and a triangle) are considered in the Hamiltonian. It is shown that the ratio of the interaction strengthF between the two kinds of interactions plays an important role in determining the critical temperature Td of phase transition from frozen to chaotic. Two methods are used to introduce the bond dilution on the Ising model on the 3–12 lattice: regular and random. The maximum of the average damage spreading 〈Dmax can approach values lower than 0.5 in both cases and the reason can be attributed to the ’survivors’ among the spins. We have also, for the first time, presented the phase diagram of the mixed G-K dynamics in the 3–12 lattice which shows what happens when going from pure Glauber to pure Kawasaki

    • Lattice specific heat and local density of states of Ni-based dilute alloys at low temperature

      P D Semalty Kapil Dev P N Ram

      More Details Abstract Fulltext PDF

      A detailed theoretical study of the low-temperature lattice specific heat of Ni-based dilute alloys has been carried out. Lattice Green’s function method has been used to calculate the local density of states of substitutional impurities and lattice specific heat in different alloys. The resonance condition has been investigated for possible occurrence of resonance modes. Except in NiCr and NiMn, low-frequency resonance modes have been obtained in all the alloys. However, no localized mode was obtained. The impurity-induced increase in lattice specific heat is explained on the basis of the obtained resonance modes. The calculation shows an excellent agreement with the measured lattice specific heat in these alloys

    • A study on electrodeposited NixFe1−x alloy films

      M Bedir O F Bakkaloğlu I H Karahan M Öztaş

      More Details Abstract Fulltext PDF

      NixFe1−x (0.22 ≤x ≤ 0.62) alloy films were grown by electrodeposition technique. A shift in diffraction peaks of NiFe and Ni3Fe was detected with increasing Ni content. The highest positive magnetoresistance ratio was detected as 5% in Ni0.51Fe0.49. Positive and negative anisotropic magnetoresistance were observed in longitudinal and transverse geometries respectively. The highest anisotropic magnetoresistance ratio of 9.8% was also detected in Ni0.51Fe0.49. The angular variation of magnetoresistance was studied. Magnetisation loop curves show that NiFe alloy films have a linear decreasing anisotropy constant with increasing Ni deposit content and show a decreasing behavior of coercivity which indicates soft magnetic property with increasing Ni deposit content

    • The isospin admixture of the ground state and the properties of the isobar analog resonances in medium and heavy mass nuclei

      D I Salamov T Babacan A Kücükbursa S Unlü I Mara˙s

      More Details Abstract Fulltext PDF

      Within the framework of quasiparticle random phase approximation (QRPA), Pyatov-Salamov method [23] for the self-consistent determination of the isovector effective interaction strength parameter, restoring a broken isotopic symmetry for the nuclear part of the Hamiltonian, is used. The isospin admixtures in the ground state of the parent nucleus, and the isospin structure of the isobar analog resonance (IAR) state were investigated with the inclusion of the pairing correlations between nucleons for the medium and heavy mass regions: 80 <A < 90, 102 <A < 124, and 204 <A < 214. It was determined that the influence of the pairing interaction between nucleons on the isospin admixtures in the ground state and the isospin structure of the IAR state is more pronounced for the light isotopes (N ≈ Z) of the investigated nuclei

    • Study of photon-induced L3 vacancy alignment for elements La to U

      Ajay Sharma Meenu Singh Raj Mittal

      More Details Abstract Fulltext PDF

      Alignment of photon-induced L3 vacancies is studied in rare earth and highZ elements at energies of experimental interest, near thresholds to 60 keV, under nonrelativistic dipole approximation. Numerical calculations of the matrix element are undertaken to produce theoretical data for comparison with the experimental findings. The A2 values being s>0.1 at photoelectron energies <20 keV are certainly higher than 5–8% uncertainties quoted in experimental results. Present findings are from a very basic model, hydrogen-like and can further be treated as reference to observe the impact of screening, relativistic, multipole and retardation corrections to the model

    • Electron impact single ionization of mono- and di-positive ions

      M Alfaz Uddin A K F Haque M S Mahbub K R Karim A K Basak

      More Details Abstract Fulltext PDF

      The electron impact ionization cross-sections of mono- and di-positive ionic targets are calculated using a second version of the modified binary-encounter-dipole (MBED) model, previously reported [M A Uddinet al, J. Phys.B37, 1909 (2004)]. The present version differs from the previous one in the scale factor of the Burgess denominator and is applicable to targets with chargesq = 1 and 2. The MBED in the present form is found to work well for 11 ionic targets ranging from Be+ to K+ and complements its previous version valid for targets withq s> 2

    • On solving energy-dependent partitioned eigenvalue problem by genetic algorithm: The case of real symmetric Hamiltonian matrices

      Rahul Sharma Subbajit Nandy S P Bhattacharyya

      More Details Abstract Fulltext PDF

      An energy-dependent partitioning scheme is explored for extracting a small number of eigenvalues of a real symmetric matrix with the help of genetic algorithm. The proposed method is tested with matrices of different sizes (30 × 30 to 1000 × 1000). Comparison is made with Löwdin’s strategy for solving the problem. The relative advantages and disadvantages of the GA-based method are analyzed

    • Subject Index of Volume 66

      More Details Abstract Fulltext PDF
    • Author Index of Volume 66

      More Details Abstract Fulltext PDF
    • Contents - Volume 66

      More Details Abstract Fulltext PDF
  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.