Massive Hyper-Kahler Sigma Models and BPS Domain Walls

With the non-Abelian Hyper-Kahler quotient by U(M) and SU(M) gauge groups, we give the massive Hyper-Kahler sigma models that are not toric in the N=1 superfield formalism. The U(M) quotient gives N!/[M! (N-M)!] (N is a number of flavors) discrete vacua that may allow various types of domain walls, whereas the SU(M) quotient gives no discrete vacua. We derive BPS domain wall solution in the case of N=2 and M=1 in the U(M) quotient model.Comment: 16 pages, 1 figure, contribution to the Proceedings of the International Conference on "Symmetry Methods in Physics (SYM-PHYS10)" held at Yerevan, Armenia, 13-19 Aug. 200

The role of infrared divergence for decoherence

Continuous and discrete superselection rules induced by the interaction with the environment are investigated for a class of exactly soluble Hamiltonian models. The environment is given by a Boson field. Stable superselection sectors emerge if and only if the low frequences dominate and the ground state of the Boson field disappears due to infrared divergence. The models allow uniform estimates of all transition matrix elements between different superselection sectors.Comment: 11 pages, extended and simplified proo

Lithium production on a low-mass secondary in a black hole soft X-ray transient

We examine production of Li on the surface of a low-mass secondary in a black hole soft X-ray transient (BHSXT) through the spallation of CNO nuclei by neutrons which are ejected from a hot (> 10 MeV) advection-dominated accretion flow (ADAF) around the black hole. Using updated binary parameters, cross sections of neutron-induced spallation reactions, and mass accretion rates in ADAF derived from the spectrum fitting of multi-wavelength observations of quiescent BHSXTs, we obtain the equilibrium abundances of Li by equating the production rate of Li and the mass transfer rate through accretion to the black hole. The resulting abundances are found to be in good agreement with the observed values in seven BHSXTs. We note that the abundances vary in a timescale longer than a few months in our model. Moreover, the isotopic ratio Li6/Li7 is calculated to be about 0.7--0.8 on the secondaries, which is much higher than the ratio measured in meteorites. Detection of such a high value is favorable to the production of Li via spallation and the existence of a hot accretion flow, rather than an accretion disk corona system in quiescent BHSXT.Comment: 4 pages, 3 figures, and 2 tables, submitted to Astrophyscal Jounal Letter

Bottom-up fabrication of Si nanodot transistors using the nc-Si dots solution

A new approach to fabricate nanometer-scale silicon devices is recently attracting much attention, which combines the conventional top-down silicon processing techniques and the bottom-up assembly of silicon nanodots, whose structures are controlled on the atomic scale. This technique enables to investigate the electronic states and transport properties of strongly-coupled multiple nanodots which will be crucial particularly for quantum information device applications. Various unique properties have been studied in such systems. For example, electrostatic interactions have been investigated for double Si dots [1] and for the two-dimensional Si multidots [2]. Coherent wavefunction coupling and associated quasi-molecular states have also been observed for a tunnel-coupled double Si nanodots [3]. In addition, metal-insulator transition has been investigated for an artificial lattice of self-organized nano-paraticles [4]. In this paper we propose and examine a novel technique of fabricating nanoscale transistors with a Si nanodot cluster as a channel based on the self-assembly of the nanocrystalline Si dots from the solution on the patterned SOI substrates

Carbon fibre tips for scanning probe microscopy based on quartz tuning fork force sensors

We report the fabrication and the characterization of carbon fibre tips for their use in combined scanning tunnelling and force microscopy based on piezoelectric quartz tuning fork force sensors. We find that the use of carbon fibre tips results in a minimum impact on the dynamics of quartz tuning fork force sensors yielding a high quality factor and consequently a high force gradient sensitivity. This high force sensitivity in combination with high electrical conductivity and oxidation resistance of carbon fibre tips make them very convenient for combined and simultaneous scanning tunnelling microscopy and atomic force microscopy measurements. Interestingly, these tips are quite robust against occasionally occurring tip crashes. An electrochemical fabrication procedure to etch the tips is presented that produces a sub-100 nm apex radius in a reproducible way which can yield high resolution images.Comment: 14 pages, 10 figure

NaV2O4: a Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains

NaV2O4 crystals were grown under high pressure using a NaCl flux, and the crystals were characterized with X-ray diffraction, electrical resistivity, heat capacity, and magnetization. The structure of NaV2O4 consists of double chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic, with the resistivity perpendicular to the chains more than 20 times greater than that parallel to the chains. Magnetically, the intrachain interactions are ferromagnetic and the interchain interactions are antiferromagnetic; 3D antiferromagnetic order is established at 140 K. First principles electronic structure calculations indicate that the chains are half metallic. Interestingly, the case of NaV2O4 seems to be a quasi-1D analogue of what was found for half-metallic materials.Comment: 14 pages, including 4 figures and 1 table, accepted for publication in PR

Fermi Surface and Anisotropic Spin-Orbit Coupling of Sb(111) studied by Angle-Resolved Photoemission Spectroscopy

High-resolution angle-resolved photoemission spectroscopy has been performed on Sb(111) to elucidate the origin of anomalous electronic properties in group-V semimetal surfaces. The surface was found to be metallic despite the semimetallic character of bulk. We clearly observed two surface-derived Fermi surfaces which are likely spin split, demonstrating that the spin-orbit interaction plays a dominant role in characterising the surface electronic states of group-V semimetals. Universality/disimilarity of the electronic structure in Bi and Sb is discussed in relation to the granular superconductivity, electron-phonon coupling, and surface charge/spin density wave.Comment: 4 pages, 3 figures. to be published in Phys. Rev. Let

Exact Eigenstates of Tight-Binding Hamiltonians on the Penrose Tiling

We investigate exact eigenstates of tight-binding models on the planar rhombic Penrose tiling. We consider a vertex model with hopping along the edges and the diagonals of the rhombi. For the wave functions, we employ an ansatz, first introduced by Sutherland, which is based on the arrow decoration that encodes the matching rules of the tiling. Exact eigenstates are constructed for particular values of the hopping parameters and the eigenenergy. By a generalized ansatz that exploits the inflation symmetry of the tiling, we show that the corresponding eigenenergies are infinitely degenerate. Generalizations and applications to other systems are outlined.Comment: 24 pages, REVTeX, 13 PostScript figures include

Espacialização da precipitação e erosividade na Bacia Hidrográfica do Rio Dourados - MS.

A distribuição da precipitação numa bacia hidrográfica durante o ano é um dos fatores determinantes para quantificar a necessidade de irrigação de culturas e de abastecimento de água doméstico e industrial, além de estudos para o controle de inundações e da erosão do solo. O potencial da chuva em causar erosão hídrica pode ser avaliado por meio de índices que se baseiam nas características físicas das chuvas de cada região, entre os quais se destacam índice de erosividade. Analisaram-se, neste trabalho, a espacialização da precipitação pluvial e o índice de erosividade médio anual e mensal na Bacia Hidrográfica do Rio Dourados. Analisando os resultados obtidos, foi possível concluir que: o regime de precipitação apresenta oscilação unimodal, com período chuvoso compreendido entre os meses de outubro e março; todos os meses da estação chuvosa apresentam drásticas reduções da precipitação média; a erosividade média anual variou de 3.192,0 a 4.977,0 MJ mm ha-1 h-1 ano-1; e os meses de dezembro a janeiro apresentam os maiores riscos de ocorrência de perdas de solo por erosão hídrica

Applying System Dynamics Approach to the Fast Fashion Supply Chain: Case Study of an SME in Indonesia

The fashion industry is the biggest contributor among the 14 creative industries in Indonesia. Nowadays many apparel companies are shifting toward the vertical integration. Since speed is everything to be successful in the apparel industry, fast fashion retailers must quickly respond to the market demand. This papers aims to develop a model of the supply chain of a small and medium scale enterprise (SME) of an apparel company in Indonesia and to propose a decision support system using System Dynamics (SD) and helps the management to identify the best business strategy. Simulated scenarios can help the management to identify the most appropriate policy to be applied in the future. Case study method was used in this research where data were collected from a typical fast fashion firm in Indonesia that produces its own wares ranging from raw materials to be ready-to-wear clothes, has three stores, a warehouse and is running online sales system. We analyses the result of many simulations in a fashion company from an operational point of view and from them we derive suggestions about the future business strategy in a small and medium fashion company in Indonesia