Results 281 to 290 of about 100,146 (306)
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The coupled-pair approximation in a basis of independent-pair natural orbitals
Chemical Physics Letters, 1976Abstract A computational method based on a rapidly convergent form of the unlinked cluster expansion is presented. Ciźek's coupled-pair approximation (CPA) is derived in a basis of partially non-orthogonal orbitals which transform each pair function to diagonal form; this produces a simple (non-variational) set of equations from which may be ...
Peter R. Taylor +3 more
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SD-pair structure in the pair approximation of the nuclear shell model
Science China Physics, Mechanics and Astronomy, 2010In this paper we study the structure coefficients of collective pairs with spin zero and spin two (SD) in a number of configurations by a few realistic nuclei. We investigate the robustness of these structure coefficients with respect to different configurations and the evolution of SD-pair structure coefficients with valence nucleon number.
Yang Lei +3 more
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Description of the even samarium isotopes in the collective pair approximation
Physical Review C, 1984A microscopic multi-j shell calculation is performed to describe the structure of the ground states of the even Sm isotopes within the pairing plus quadrupole model and in the collective pair approximation. Agreement with the experimental data is found for both quadrupole deformation ..beta.. and for the diffusivity of the Fermi surface.
F. CATARA +3 more
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Number-operator approximation for pairing
Physical Review C, 1983Conservation of particle number in the number-operator approximation of Otsuka and Arima is shown to require a particular normalization for the pair-creation operator. Even with this normalization, two difficulties arise: (a) the average number of particles in a shell can easily violate the Pauli principle, and (b) the mean square fluctuation of the ...
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Pair Approximations of Takeover Dynamics in Regular Population Structures
Evolutionary Computation, 2009In complex adaptive systems, the topological properties of the interaction network are strong governing influences on the rate of flow of information throughout the system. For example, in epidemiological models, the structure of the underlying contact network has a pronounced impact on the rate of spread of infectious disease throughout a population.
Joshua L. Payne, Margaret J. Eppstein
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Microscopic description of β-band in the collective pair approximation
Nuclear Physics A, 1983Abstract The collective pair approximation, previously used in the description of the ground-state band in deformed nuclei, is extended to the description of the β-band. This is obtained by promoting to an excited state one of the basic pairs defining the ground-state condensate in the intrinsic frame. The microscopic structure of the excited pair is
MAGLIONE, ENRICO +3 more
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Random-field Ising model in the pair approximation
Physical Review B, 1988The random-field Ising model is studied in the pair approximation. Second-order transition lines and tricritical points are obtained for the bimodal (sum of two \ensuremath{\delta} functions) random-field distributions. When the number of interacting nearest-neighbor spins z is 3, no tricritical point appears.
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Pair-edge approximation for heterogeneous lattice population models
Theoretical Population Biology, 2003Stephen P Ellner
exaly