400 research outputs found
Nuclear Mean Fields through Selfconsistent Semiclassical Calculations
Semiclassical expansions derived in the framework of the Extended
Thomas-Fermi approach for the kinetic energy density tau(r) and the spin-orbit
density J(r) as functions of the local density rho(r) are used to determine the
central nuclear potentials V_n(r) and V_p(r) of the neutron and proton
distribution for effective interactions of the Skyrme type. We demonstrate that
the convergence of the resulting semiclassical expansions for these potentials
is fast and that they reproduce quite accurately the corresponding Hartree-Fock
average fields.Comment: LATEX, 25 pages, including 11 eps figures. to be published in Europ.
Phys. Journal
Temperature dependence of persistent spin currents in a spin-orbit-coupled electron gas: A density-matrix approach
URL:http://link.aps.org/doi/10.1103/PhysRevB.77.155315
DOI:10.1103/PhysRevB.77.155315We present a simple analytical method, based on the canonical density matrix, for the calculation of the equilibrium spin current as a function of temperature in a two- dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling terms. We find that the persistent spin current is extremely robust against thermal disorder: its variation with temperature is exponentially small (âeâTFâT) at temperatures much smaller than the Fermi temperature TF and changes to a power law TFâT for TâȘąTF
Airy gas model: From three to reduced dimensions
By using the propagator of linear potential as a main tool, we extend the
Airy gas model, originally developed for the three-dimensional () edge
electron gas, to systems in reduced dimensions (). First, we derive
explicit expressions for the edge particle density and the corresponding
kinetic energy density (KED) of the Airy gas model in all dimensions. The
densities are shown to obey the local virial theorem. We obtain a functional
relationship between the positive KED and the particle density and its
gradients and analyze the results inside the bulk as a limit of the
local-density approximation. We show that in this limit the KED functional
reduces to that of the Thomas-Fermi model in dimensions
Ultraslow light propagation in an inhomogeneously broadened rare-earth ion-doped crystal
We show that Coherent Population Oscillations effect allows to burn a narrow
spectral hole (26Hz) within the homogeneous absorption line of the optical
transition of an Erbium ion-doped crystal. The large dispersion of the index of
refraction associated with this hole permits to achieve a group velocity as low
as 2.7m/s with a ransmission of 40%. We especially benefit from the
inhomogeneous absorption broadening of the ions to tune both the transmission
coefficient, from 40% to 90%, and the light group velocity from 2.7m/s to
100m/s
Scalable multimode entanglement based on efficient squeezing of propagation eigenmodes
Continuous-variable encoding of quantum information in the optical domain has
recently yielded large temporal and spectral entangled states instrumental for
quantum computing and quantum communication. We introduce a protocol for the
generation of spatial multipartite entanglement based on phase-matching of a
propagation eigenmode in a monolithic photonic device: the array of quadratic
nonlinear waveguides. We theoretically demonstrate in the spontaneous
parametric downconversion regime the generation of large multipartite entangled
states useful for multimode quantum networks. Our protocol is remarkably simple
and robust as it does not rely on specific values of coupling, nonlinearity or
length of the sample.Comment: 8 pages, 5 figures, title modified and new results added. Accepted
for publication in Physical Review Researc
Sorption Study of a Basic Dye âGentian Violetâ from Aqueous Solutions Using Activated Bentonite
AbstractVarious industries like textiles, papers, food, plastics, leather, etc are great water and organic colorant users. Hence, the resulting effluents could be an important source of environmental problems, since they may contain stable and non biodegradable contaminants, like organic dyes. The treatment of which is the main scope of the present study. Different ways of dye removal from these effluents do exist, such as flotation, reverse osmosis, chemical flocculation and adsorption etc. Adsorption is used in this work for the removal of a particular basic dye, known as Gentian violet (GV) from an aqueous solution, by means of a natural clay material. The influence of various key parameters like contact time, temperature, ionic strength, etc. on the adsorbed amount of the dye was investigated, for batch conditions. A kinetic study was also carried out, the obtained experimental results were tested against the pseudo first order and the pseudo second order equations. An analysis of the obtained equilibrium data showed that the dye adsorption is best described by the Langmuir model. The obtained results showed that temperature did enhance the Gentian violet dye retention process onto the considered bentonite whereas the obtained thermodynamic parameters indicated that the adsorption process is spontaneous and endothermic. The simultaneous presence of methylene blue, which is another colorant compound, with the Gentian violet was also considered. The clay materials showed a better affinity for the first one i e. methylene blue. In conclusion and according to the obtained results, the clay material may be recommended as an industrial adsorbent for the treatment of effluents containing Gentian violet (GV)
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