No abstract available

No abstract available

No abstract available

No abstract available

[en] We present here a reformulation of the Fermi-liquid theory for the periodic Anderson model (for the particular case of the simplest type of Anderson Hamiltonian) in a basis in which c and f electrons are explicitly distinguished. We show that provided the system is normal, i.e., the f-electron self-energy is analytic in momentum and frequency near the Fermi wave vectors and Fermi energy, respectively, all quasiparticle parts of the response functions of the system reduce to the form as expected from our usual understanding of a Fermi liquid. In doing so we also show the validity of a kinetic equation, and are able to obtain formal formulas for the physical quantities that a quasiparticle carries when the corresponding quantities for the original electrons are given. We point out however that the value of these quantities, and also the nonquasiparticle part of the response, can in general be rather different from a too naive understanding to a single-component Fermi liquid

[en] We have nearly tripled the range of magnetic field strength over which bulk three-body recombination has been studied in spin-polarized atomic hydrogen. Analysis of our data (8--20 T) shows for the first time a qualitative agreement with theoretical predictions for the field dependence of dipolar recombination. Our results for the three-body exchange recombination are over an order of magnitude lower than a previously published value, and thus in reasonable agreement with theory. We discuss the prospects for observing Bose-Einstein condensation in very high magnetic fields

[en] A Monte Carlo model simulating atmospheric transport and diffusion in the PBL is presented. In a previous study, it was shown that it works well in homogeneous turbulence and fits well the Willis and Deardorff water tank simulations in convective nonhomogeneous conditions. In the present paper a sensivity analysis aimed at estimating the importance and effectiveness of the model parameters is performed and discussed. Our model makes use of Hanna's scheme for the vertical structure of the turbulent parameters, and of an empirical parametrization of updrafts and downdrafts in convective unstable condictions. Emitting the particles either from a point source or uniformly distributed along the vertical it is found that the model avoids the particle accumulation at the top and bottom of the PBL and recovers the Eulerian turbulent statistics. This demonstrates that our numerical scheme is consistent with the physical constraints, i.e. mass and energy are preserved and an initial uniform distribution remains so. Finally it is shown that considering the contribution of the cross-correlation term, mean value of u'w', does not improve significantly the model performances

[en] The results of numerical calculations, performed in the spherical geometry, of FQHE states of N ≤ 12 electrons on the lowest Landau level at filling ν = 1/2, are presented. The extrapolated value for the energy per particle is -0.469±0.005, in the usual units e²/a₀. Densities and pair correlation functions of the ground states are computed. The pair correlation are 'Wigner-crystal-like', with maxima corresponding to regular polyhedra. For N=4, 8 and 10 it is found that the system presents a broken rotational invariance which generalizes the broken particle-hole symmetry already known in different gauges. Quasi-particles, quasi-holes and the 'exciton' spectrum are computed, and some microscopic wave functions are examined. The quasi-particles and the quasi-holes are not localized; this suggests a possible 'deformability' of the system

[en] The cause of the ringing instability in particle-in-cell (PIC) fluid calculations is identified, and its properties are studied. The ringing instability is caused by aliasing, just as is the finite grid instability previously identified in PIC plasma simulation, and results in large amplitude fluctuations in the particle density. The instability occurs when the flow speed drops below a critical value, which is lower with higher order interpolation and zero with Gaussian interpolation. The instability growth rate is only weakly dependent on the number of particles per cell, but appears to be suppressed by implicit differencing in time. copyright 1988 Academic Press, Inc

[en] The line shape for high-momentum-transfer neutron scattering experiments on quantum fluids is derived by a novel perturbative method which includes the effect of the spatial correlations in the ground state. The final-state broadening of the impulse approximation is shown to be non-Lorentzian, to have a zero second moment, and to be significant for all feasible experiments. There are important implications for the goal of measuring momentum distributions. Numerical results are presented for ⁴He