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A New Microscopic Calculation for the Uniform Electron Fluid

100%
Bouchebak A., Al-Sugheir M., Ghassib H.
Acta Physica Polonica A
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2011
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vol. 119
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issue 3
312-322
EN
The static fluctuation approximation is applied for the first time to an electronic system. A simple model (a uniform electron fluid) is chosen to explore the applicability of static fluctuation approximation to electrons in metals. The thermodynamic properties - the internal energy per particle, the pressure, the entropy per unit volume, the heat capacity per unit volume, and the chemical potential - are calculated over a wide range of densities within the metallic-density region. Finally, the pair-correlation function for the electron fluid is evaluated. Values of this function are then tabulated for zero-interparticle separation at several densities of interest. The results of this work are found to be in good agreement with several other many-body calculations.
2
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Bose-Einstein Condensation of Hard Sphere Homogeneous Gas in Static Fluctuation Approximation

100%
Al-Sugheir M., Gasymeh S., Shatnawi M., Bawa'aneh M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 2
154-156
EN
The condensation fraction, transition temperature, and energy per particle for a hard sphere interacting homogeneous Bose gas using the static fluctuation approximation have been determined. The transition temperature at liquid helium density has been found to be lower than that for the noninteracting gas. Both superfluidity and the Bose-Einstein condensation have been found to occur at the same transition temperature. Our results are consistent with results obtained by other methods.
3
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Weak ^{3}He Pairing in ^{3}He-He(II) Mixtures

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Sandouqa A., Joudeh B., Al-Sugheir M., Ghassib H.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6
807-813
EN
In this paper a theoretical study of a possible phase transition in dilute ^3He-He(II) mixtures is presented using the Galitskii-Migdal-Feynman formalism. The effective scattering length is calculated from the Galitskii-Migdal-Feynman T-matrix, which is essentially the effective scattering amplitude dependent on the medium. It is found that at very low ^3He concentrations the s-wave effective scattering length for ^3He-He(II) varies discontinuously from positive to negative values at some critical concentration. This indicates a crossover from a regime with dimers to another with the Cooper pairs. The binding energy of the weakly-bound dimers ^3He_2 is computed. The effective p-wave scattering lengths are calculated and compared to the effective s-wave scattering lengths at low and high concentrations. It is found that p-scattering has an important effect on the instability of these mixtures at concentrations x > 1%. Finally, the transport coefficients are computed and compared to the theoretical predictions of Fu and Pethick and the experimental results of König and Pobell.
4
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A Microscopic Study of One-Dimensional Solid ^4He Using the Static Fluctuation Approximation

100%
Alhami E., Al-Sugheir M., Ghassib H.
Acta Physica Polonica A
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2015
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vol. 127
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issue 6
1648-1656
EN
In this work, solid helium is studied within the framework of the static fluctuation approximation. The closed set of nonlinear coupled equations, which is an inherent feature of this approximation, is derived for one-dimensional solid ^{4}He. This set is solved numerically by an iteration method for a realistic interhelium potential. The central aim is to determine the chemical potential μ , condensate fraction N_{0}/N, total energy U, heat capacity C, and entropy S of the system. The effects of temperature T, total number of particles N, frequency ω and lattice constant R on these properties are emphasized and explained. Below 80 mK: (1) as N or ω increases, μ increases; (2) as N increases, U, C, and S increase; whereas N_{0}/N, U/N, C/Nk_{B} and S/Nk_{B} decrease (k_{B} being Boltzmann's constant); (3) as ω increases, N_{0}/N, U, C, and S increase; whereas U/N, C/Nk_{B} and S/Nk_{B} are hardly affected; and (4) as T → 0, the effect of R on N_{0}/N increases. These results are presented in a set of figures.
5
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On the Effects of the Interaction Potential Parameters on Bose-Einstein Condensation

100%
Al-Sugheir M., Al-Khzon H., Al-Maghrabi M., Alna'washi G.
Acta Physica Polonica A
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2012
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vol. 122
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issue 4
704-708
EN
In this work the effect of the potential parameters on the condensate fraction and the critical temperature of neutral many-bosonic system are investigated. A many-body technique called the static fluctuation approximation is used in this study. The interaction potential is modeled by two linear terms. The condensation fraction and critical temperature were found to decrease with increasing the strength or the range of the repulsive part of the potential. On the other hand, the condensation fraction and critical temperature increase with increasing the depth or range of the attractive part of the potential.
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