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[en] We present the analytical results at the mean-field level for the asymmetrical fermion system with attractive contact interaction at zero temperature. The results can be expressed in terms of linear combinations of the elliptic integrals of the first and second kinds. In the limit of small gap parameter, we discuss how the asymmetry in fermion species affects the phases of the ground state of the system. In the limit of large gap parameter, we show that two candidate phases are competing for the system's ground state. The Sarma phase containing a pure Fermi fluid and a mixed condensate is favored at a large degree of asymmetry. The separated phase consisting of a pure Fermi fluid and a boson condensate supports the system at a small degree of asymmetry. The two phases are degenerate in the limit of infinite pairing gap
[en] We compute binding energies and root-mean-square radii for weakly bound systems of N=4 and 5 identical bosons. Ground and first excited states of an N-body system appear below the threshold for binding the system with N-1 particles. Their root-mean-square radii approach constants in the limit of weak binding. Their probability distributions are on average located in nonclassical regions of space which result in universal structures. Radii decrease with increasing particle number. The ground states for more than five particles are probably nonuniversal, whereas excited states may be universal.
[en] We extend to finite temperature a Green's-function method that was previously proposed to evaluate ground-state properties of mesoscopic clouds of noninteracting fermions moving under harmonic confinement in one dimension. By calculations of the particle and kinetic-energy density profiles, we illustrate the role of thermal excitations in smoothing out the quantum shell structure of the cloud and in spreading the particle spill out from quantum tunnel at the edges. We also discuss the approach of the exact density profiles to the predictions of a semiclassical model often used in the theory of confined atomic gases at finite temperature
[en] The constrained minimization independent-fermion kinetic-energy kernel, δ2Ts[ρ]/δρ(r)δρ(r'), has a zero mode for all ρ(r), while it is non-negative for ρ(r) noninteracting v representable. copyright 1996 The American Physical Society
[en] The complete O(α2) correction to the long-range interaction between neutral closed-shell atoms is obtained, the relation to the asymptotic expansion of the known short-range interaction at the atomic scale is presented and a general interaction potential that is valid in the whole range of the interatomic distances is constructed
[en] We have carried out a comprehensive study of electron impact on the open-chain S3 isomer by using the R-matrix method. Elastic (integrated and differential), momentum-transfer, excitation, and ionization cross sections, along with effective collision frequency over a wide electron temperature range (500-30 000 K) have been presented. The target states are represented by including correlations via a configuration interaction technique. The results of the static-exchange, correlated 1-state, and 24-state close-coupling approximations are presented. Our study has detected a shape resonance, six core-excited shape resonances, and one Feshbach resonance in the 24-state model. We detect a stable bound state of S3- of 2B1 symmetry having a configuration ...11a12,...3b124b1,...8b22,...2a22, with a vertical electronic affinity value of 2.15 eV, and a ionization potential value of 9.77 eV, which are in good agreement with the experimental values of 2.093±0.025 and 9.68±0.03 eV, respectively. The ionization cross sections are calculated using the binary-encounter-Bethe model in which Hartree-Fock molecular orbitals at a self-consistent level are used to calculate kinetic and binding energies of the occupied molecular orbitals. We have used partial waves up to l=4 to represent continuum electron in our R-matrix method. A Born top-up procedure is invoked to account for the contribution of partial waves higher than l=4 to obtain converged cross sections.
[en] An analytic expression is presented for the elementary excitation spectrum of the Bose-Einstein condensate of a trapped boson system in the weakly interacting, low-density limit. Explicit analytic formulas for the elementary excitation spectrum are obtained for harmonic-oscillator traps. These formulas provide information about the behavior of the elementary excitation levels as a function of the number of atoms and their interaction strength for a given trap geometry. They also provide a low-density benchmark for results of fully numerical calculations. copyright 1997 The American Physical Society
[en] We present a statistical fragmentation study of the C5, C7, and C9 carbon clusters using the Metropolis Monte Carlo and Weisskopf methods. We show that inclusion of several isomeric forms as well as rotational effects is essential to reproduce the experimental observations. We have found that, for cluster excitation energies around 10 eV, several fragmentation channels are efficiently populated, but the dominant one always corresponds to Cn-3/C3. For high enough excitation energies, we observe first-order phase transitions corresponding to a complete breakup of the cluster