14,719 research outputs found

    Self-consistent calculation of the coupling constant in the Gross-Pitaevskii equation

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    A method is proposed for a self-consistent evaluation of the coupling constant in the Gross-Pitaevskii equation without involving a pseudopotential replacement. A renormalization of the coupling constant occurs due to medium effects and the trapping potential, e.g. in quasi-1D or quasi-2D systems. It is shown that a simplified version of the Hartree-Fock-Bogoliubov approximation leads to a variational problem for both the condensate and a two-body wave function describing the behaviour of a pair of bosons in the Bose-Einstein condensate. The resulting coupled equations are free of unphysical divergences. Particular cases of this scheme that admit analytical estimations are considered and compared to the literature. In addition to the well-known cases of low-dimensional trapping, cross-over regimes can be studied. The values of the kinetic, interaction, external, and release energies in low dimensions are also evaluated and contributions due to short-range correlations are found to be substantial.Comment: 15 pages, ReVTEX, no figure

    Kinetic energy of Bose systems and variation of statistical averages

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    The problem of defining the average kinetic energy of statistical systems is addressed. The conditions of applicability for the formula, relating the average kinetic energy with the mass derivative of the internal energy, are analysed. It is shown that incorrectly using this formula, outside its region of validity, leads to paradoxes. An equation is found for a parametric derivative of the average for an arbitrary operator. A special attention is paid to the mass derivative of the internal energy, for which a general formula is derived, without invoking the adiabatic approximation and taking into account the mass dependence of the potential-energy operator. The results are illustrated by the case of a low-temperature dilute Bose gas.Comment: Latex, 11 page

    Keys to families of Cladocera and to subfamilies, genera, species and subspecies of Macrothricidae and Moinidae [Translation from: Leningrad, Fauna SSSR, Crustacea 1 (3), 1971]

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    Identification keys to families of Cladocera and to subfamilies, genera, species and subspecies of Macrothricidae and Moinidae are given. This translation does not include ecological notes or illustrations

    Sensory Contact Model: Protocol, Control, Applications

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    Among the models that become more and more popular in behavioral neuroscience are biosocial models, which allow studying the consequences of chronic social conflicts and social stress in animals. The sensory contact model appears to represent one of such models. Repeated experience of aggression or social defeats in daily agonistic interactions in male mice of different strains leads to the formation of opposing kinds of social behavior: one attributable to winners (aggressors) and another attributable to losers (defeated males, victims of aggression). A large variety of behavioral pathologies which develop in male mice in these conditions (anxious depression, catalepsy, social withdrawal, pronounced aggression, anxiety, hyperactivity, cognitive disturbances, anhedonia etc.), which are accompanied by somatic changes (reduced gonad function, psychogenic immune deficiency etc), suggest that this approach could be used for different aims of biomedical studies. Putative mechanisms of release and maintenance of aggressive and submissive behaviors in male mice under the sensory contact model, criteria of correct application, basic experimental setups and problem of the control, methodical capabilities and potentials of the sensory contact model applications are discussed in this paper

    ππ\pi\pi scattering S wave from the data on the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n

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    The results of the recent experiments on the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 ππ\pi\pi S wave phase shift δ00\delta^0_0 and inelasticity η00\eta^0_0 a new set of data is obtained. Difficulties emerging when using the physical solutions for the π0π0\pi^0\pi^0 S and D wave amplitudes extracted with the partial wave analyses are discussed. Attention is drawn to the fact that, for the π0π0\pi^0\pi^0 invariant mass, m, above 1 GeV, the other solutions, in principle, are found to be more preferred. For clarifying the situation and further studying the f0(980)f_0(980) resonance thorough experimental investigations of the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n in the m region near the KKˉK\bar K threshold are required.Comment: 17 pages, 5 figure

    Number-of-particle fluctuations in systems with Bose-Einstein condensate

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    Fluctuations of the number of particles for the dilute interacting gas with Bose-Einstein condensate are considered. It is shown that in the Bogolubov theory these fluctuations are normal. The fluctuations of condensed as well as noncondensed particles are also normal both in canonical and grand canonical ensembles.Comment: Latex file, 12 page

    Analysis of the nature of the ϕγπη\phi\to\gamma\pi\eta and ϕγπ0π0\phi\to\gamma\pi^0\pi^0 decays

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    We study interference patterns in the ϕ(γa0+π0ρ)γπη\phi\to(\gamma a_0+\pi^0\rho)\to\gamma\pi\eta and ϕ(γf0+π0ρ)γπ0π0\phi\to(\gamma f_0+\pi^0\rho)\to\gamma \pi^0\pi^0 reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the π0η\pi^0\eta spectrum in the decay ϕγπη\phi\to\gamma\pi\eta everywhere over the energy region and does not distort the π0π0\pi^0\pi^0 spectrum in the decay ϕγπ0π0\phi\to\gamma\pi^0\pi^0 in the wide region of the π0π0\pi^0\pi^0 system invariant mass, mππ>670m_{\pi\pi}>670 MeV, or when the photon energy is less than 300 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are reasonable arguments in favor of the one-loop mechanism ϕK+Kγa0\phi\to K^+K^-\to\gamma a_0 and ϕK+Kγf0\phi\to K^+K^-\to\gamma f_0. We discuss also distinctions between the four-quark, molecular, and two-quark models and argue that the Novosibirsk data give evidence in favor of the four-quark nature of the scalar a0(980)a_0(980) and f0(980)f_0(980) mesons.Comment: 15 pages, 7 figures, title is changed, a few clarifying remarks are added, accepted for publication in Physical Review

    Modelling the rapid spherical compression of isotropic turbulence

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    Rapid distortion analysis is used to modify the form of the closure model for the dissipation rate of the turbulent kinetic energy. The modification is such that the evolution of the dissipation rate during a rapid compression is predicted exactly; good agreement between the model prediction and direct simulation data is obtained. Previous closure proposals fail to properly predict the rapid compression case. The reason for the difference between the present and previous models is traced to the fact that previous workers neglected variations of kinematic viscosit

    Deploying a middleware architecture for next generation mobile systems

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    Although 2G systems quite adequately cater for voice communications, today demand is for high-speed access to data centric applications and multimedia. Future networks have been designed to provide higher rates for data transmission, but this will be complemented by higher speed access to services via hotspots using secondary wireless interfaces such as Bluetooth or WLAN. With a wide range of applications that may be developed, a growing number of short range wireless interfaces that may be deployed, and with mobile terminals of different capabilities, a means to integrate all these variables in order to facilitate provision of services is desirable. This paper describes an architecture involving the use of middleware that makes software development independent of the specific wireless platfor
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