Operator-Algebraic Approach to the Yrast Spectrum of Weakly Interacting Trapped Bosons

We present an operator-algebraic approach to deriving the low-lying quasi-degenerate spectrum of weakly interacting trapped N bosons with total angular momentum \hbar L for the case of small L/N, demonstrating that the lowest-lying excitation spectrum is given by 27 g n_3(n_3-1)/34, where g is the strength of the repulsive contact interaction and n_3 the number of excited octupole quanta. Our method provides constraints for these quasi-degenerate many-body states and gives higher excitation energies that depend linearly on N.Comment: 7 pages, one figur

Pyridoxine and survival of tilapia (Sarotherodon mossambicus Peters)

Pyridoxine requirements of tilapia (Sarotherodon mossambicus Peters) were studied in two separate experiments using casein-based diets. In Experiment 1, fish on pyridoxine supplemented diet (14.0mg/100g diet) showed no adverse symptoms and remained healthy while fish on a pyridoxine-free diet showed abnormal behaviour with high mortality. Graded dietary pyridoxine (0.13 to 3.52mg/100g diet) was used in Experiment 2. Lower dietary supplementations of pyridoxine resulted in reduced weight increase, high mortality, high ratio of serum glutamate-oxal-acetate transaminase glutamate-pyruvate transaminase, and reduced blood sugar. The results suggest the dietary requirement of pyridoxine may be between 0.5g and 1.17mg/100g diet; higher supplementations did not appear to confer any further benefit

Book Reviews

Book Review 1Book Title: The Asian Elephant: Ecology and ManagementBook Author: R. SukumarCambridge University Press, 1989. Paperback edition 1991. 255 pp. ISBN: 0-521-360aO-3-XBook Review 2Book Title: Key to Parasitic NematodesBook Author: Edited by K.I. SkryabinPrinted by Amerind Publishing Co., New Delhi, distributed by E.J. Brill, Leiden, The Netherlands (1991). 4 Volumes; 1097 pages.Book Review 3Book Title: Fauna Iberica, Vol. 1. Mollusca CephalopodaBook Author: Angel Guerra SierraMuseo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Cientificas, Madrid, 1992. 327 pages and 19 colour photographs.Book Review 4Book Title: Roberts' Birds of Southern AfricaBook Author: Gordon L. Maclean6th edition 1993. John Voelcker Bird Book Fund. Cape Town.Book Review 5Book Title: Biochemical ProtozoologyBook Authors: Edited by Graham Coombs & Michael NorthTaylor & Francis Ltd, London/Washington DC 1991. 55 Chapters; 635 pages. ISBN 0-7484-0001-X.Book Review 6Book Title: The Living Deserts of Southern AfricaBook Author: Barry G. LovegroveFernwood Press, Vlaeberg (Cape Town), 1993. ISBN 0-9583154-7-7

A possible Reinterpretation of Einstein's Equations

In this paper, we first review Huei's formulation in which it is shown that the linearized Einstein equations can be written in the same form as the Maxwell equations. We eliminate some imperfections like the scalar potential which is ill linked to the electric-type field, the Lorentz-type force which is obtained with a time independence restriction and the undesired factor 4 which appears in the magnetic-type part. Second, from these results and in the light of a recent work by C.C. Barros, we propose an extension of the equivalence principle and we suggest a new interpretation for Einstein's equations by showing that the electromagnetic Maxwell equations can be derived from a new version of Einstein's ones.Comment: 11 pages, no figure

Impact of chronic consumption of dairy products varying in fatty acid composition on postprandial lipid responses: preliminary insights from the RESET study

Impact of chronic consumption of dairy products varying in fatty acid composition on postprandial lipid responses: preliminary insights from the RESET stud

Stability of Attractive Bose-Einstein Condensates in a Periodic Potential

Using a standing light wave trap, a stable quasi-one-dimensional attractive dilute-gas Bose-Einstein condensate can be realized. In a mean-field approximation, this phenomenon is modeled by the cubic nonlinear Schr\"odinger equation with attractive nonlinearity and an elliptic function potential of which a standing light wave is a special case. New families of stationary solutions are presented. Some of these solutions have neither an analog in the linear Schr\"odinger equation nor in the integrable nonlinear Schr\"odinger equation. Their stability is examined using analytic and numerical methods. Trivial-phase solutions are experimentally stable provided they have nodes and their density is localized in the troughs of the potential. Stable time-periodic solutions are also examined.Comment: 12 pages, 18 figure

Thermodynamics of an interacting trapped Bose-Einstein gas in the classical field approximation

We present a convenient technique describing the condensate in dynamical equilibrium with the thermal cloud, at temperatures close to the critical one. We show that the whole isolated system may be viewed as a single classical field undergoing nonlinear dynamics leading to a steady state. In our procedure it is the observation process and the finite detection time that allow for splitting the system into the condensate and the thermal cloud.Comment: 4 pages, 4 eps figures, final versio

Scattering of light and atoms in a Fermi-Dirac gas with BCS pairing

We theoretically study the optical properties of a Fermi-Dirac gas in the presence of a superfluid state. We calculate the leading quantum-statistical corrections to the standard column density result of the electric susceptibility. We also consider the Bragg diffraction of atoms by means of light-stimulated transitions of photons between two intersecting laser beams. Bardeen-Cooper-Schrieffer pairing between atoms in different internal levels magnifies incoherent scattering processes. The absorption linewidth of a Fermi-Dirac gas is broadened and shifted. Bardeen-Cooper-Schrieffer pairing introduces a collisional local-field shift that may dramatically dominate the Lorentz-Lorenz shift. For the case of the Bragg spectroscopy the static structure function may be significantly increased due to superfluidity in the nearforward scattering.Comment: 13 pages, 6 figures; to appear in PR

Stabilization and pumping of giant vortices in dilute Bose-Einstein condensates

Recently, it was shown that giant vortices with arbitrarily large quantum numbers can possibly be created in dilute Bose-Einstein condensates by cyclically pumping vorticity into the condensate. However, multiply quantized vortices are typically dynamically unstable in harmonically trapped nonrotated condensates, which poses a serious challenge to the vortex pump procedure. In this theoretical study, we investigate how the giant vortices can be stabilized by the application of a Gaussian potential peak along the vortex core. We find that achieving dynamical stability is feasible up to high quantum numbers. To demonstrate the efficiency of the stabilization method, we simulate the adiabatic creation of an unsplit 20-quantum vortex with the vortex pump.Comment: 8 pages, 6 figures; to be published in J. Low Temp. Phys., online publication available at http://dx.doi.org/10.1007/s10909-010-0216-

Spectral method for the time-dependent Gross-Pitaevskii equation with a harmonic trap

We study the numerical resolution of the time-dependent Gross-Pitaevskii equation, a non-linear Schroedinger equation used to simulate the dynamics of Bose-Einstein condensates. Considering condensates trapped in harmonic potentials, we present an efficient algorithm by making use of a spectral Galerkin method, using a basis set of harmonic oscillator functions, and the Gauss-Hermite quadrature. We apply this algorithm to the simulation of condensate breathing and scissors modes.Comment: 23 pages, 5 figure