Collective Excitations Spectrum in Density Modulated One-Dimensional Electron Gas in a Magnetic Field

We determine the collective excitations spectrum and discuss the numerical results for a parabolically confined density modulated quasi-one dimensional electron gas (1DEG) in the presence of an external magnetic field. We derive the inter-and intra-band magnetoplasmon spectrum within the Self Consistent Field (SCF) approach. In this work we focus on magnetoplasmon oscillations in this system and as such results are presented for the intra-Landau-band magnetoplasmon spectrum that exhibits oscillatory behavior, these oscillations are not with constant period in 1/B and are significantly effected at low B and corresponding high 1/B.Comment: 10 pages, 2 figure

ETHNO-VETERINARY PRACTICES AMONGST LIVESTOCK FARMERS IN NGAMILAND DISTRICT, BOTSWANA

We carried out a study to determine ethno-veterinary knowledge used to treat and prevent livestock diseases in Toteng Village in Ngamiland District, northwestern Botswana. Primary data were collected through simple random sampling of 45 households in Toteng. Respondents were either livestock owners or cattle herders. Respondents were interviewed using a structured questionnaire which had both open and closed-ended questions. Cattle ownership or herdership in Toteng is an inter-generational occupation with people ranging from 15 to 94 years old. Cattle were acquired either through inheritance, buying, mafisa (reciprocal exchange) system or government scheme. Women in the study area were more involved in livestock farming activities. Eleven livestock diseases were reported to be prevalent in the study area. The top six diseases were tlhako le molomo -foot and mouth disease (FMD), matlho - eye infections, letshololo-diarrhea, madi -pasteurollosis, mokokomalo - aphosphorisis and pholoso- contagious abortion. At least nine medicinal plant species having ethno-veterinary applications were recorded in the study area. Single plants are mostly used rather than a combination of plants. A number of social strategies were mentioned such as ‘go fetola mafudiso’ - to change grazing areas, and ‘go thaa lesaka’ – to ritualistically ‘protect a kraal’ or livestock against evil spells and predators (lions). Although the intervention of conventional veterinary medicine is pervasive in Toteng, and many livestock owners are resorting to it, there is evidence, however, of generalized ethno-veterinary knowledge used to treat and prevent livestock diseases. Local farmers and their herders in Ngamiland are not only knowledgeable and experienced in treating a range of livestock diseases, but also in performing other veterinary tasks such as assisting in births, treating fractures and range management strategies to mitigate particular threats from their local environment. The efficacy of ethno-veterinary knowledge for preventing and treating livestock diseases and range management strategies identified in this study need to be fully investigated and integrated in veterinary extension services

Inelastic Coulomb scattering rates due to acoustic and optical plasmon modes in coupled quantum wires

We report a theoretical study on the inelastic Coulomb scattering rate of an injected electron in two coupled quantum wires in quasi-one-dimensional doped semiconductors. Two peaks appear in the scattering spectrum due to the optical and the acoustic plasmon scattering in the system. We find that the scattering rate due to the optical plasmon mode is similar to that in a single wire but the acoustic plasmon scattering depends crucially on its dispersion relation at small $q$. Furthermore, the effects of tunneling between the two wires are studied on the inelastic Coulomb scattering rate. We show that a weak tunneling can strongly affect the acoustic plasmon scattering.Comment: 6 Postscript figure

Electronic structure of rectangular quantum dots

We study the ground state properties of rectangular quantum dots by using the spin-density-functional theory and quantum Monte Carlo methods. The dot geometry is determined by an infinite hard-wall potential to enable comparison to manufactured, rectangular-shaped quantum dots. We show that the electronic structure is very sensitive to the deformation, and at realistic sizes the non-interacting picture determines the general behavior. However, close to the degenerate points where Hund's rule applies, we find spin-density-wave-like solutions bracketing the partially polarized states. In the quasi-one-dimensional limit we find permanent charge-density waves, and at a sufficiently large deformation or low density, there are strongly localized stable states with a broken spin-symmetry.Comment: 8 pages, 9 figures, submitted to PR

Far-infrared edge modes in quantum dots

We have investigated edge modes of different multipolarity sustained by quantum dots submitted to external magnetic fields. We present a microscopic description based on a variational solution of the equation of motion for any axially symmetric confining potential and multipole mode. Numerical results for dots with different number of electrons whose ground-state is described within a local Current Density Functional Theory are discussed. Two sum rules, which are exact within this theory, are derived. In the limit of a large neutral dot at B=0, we have shown that the classical hydrodynamic dispersion law for edge waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size effects are taken into account.Comment: We have changed some figures as well as a part of the tex

Far-infrared edge modes in quantum dots

We have investigated edge modes of different multipolarity sustained by quantum dots submitted to external magnetic fields. We present a microscopic description based on a variational solution of the equation of motion for any axially symmetric confining potential and multipole mode. Numerical results for dots with different number of electrons whose ground-state is described within a local Current Density Functional Theory are discussed. Two sum rules, which are exact within this theory, are derived. In the limit of a large neutral dot at B=0, we have shown that the classical hydrodynamic dispersion law for edge waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size effects are taken into account.Comment: We have changed some figures as well as a part of the tex

Plasmon Modes and Correlation Functions in Quantum Wires and Hall Bars

We present microscopic derivations of the one-dimensional low-energy boson effective Hamiltonians of quantum wire and quantum Hall bar systems. The quantum Hall system is distinguished by its spatial separation of oppositely directed electrons. We discuss qualitative differences in the plasmon collective mode dispersions and the ground state correlation functions of the two systems which are consequences of this difference. The slowly-decaying quasi-solid correlations expected in a quantum wire are strongly suppressed in quantum Hall bar systems.Comment: 7 pages, RevTex, 3 figures and 1 table included; references updated and minor typos correcte