Three Dimensional Topological Field Theory induced from Generalized Complex Structure

We construct a three-dimensional topological sigma model which is induced from a generalized complex structure on a target generalized complex manifold. This model is constructed from maps from a three-dimensional manifold $X$ to an arbitrary generalized complex manifold $M$. The theory is invariant under the diffeomorphism on the world volume and the $b$-transformation on the generalized complex structure. Moreover the model is manifestly invariant under the mirror symmetry. We derive from this model the Zucchini's two dimensional topological sigma model with a generalized complex structure as a boundary action on $\partial X$. As a special case, we obtain three dimensional realization of a WZ-Poisson manifold.Comment: 18 page

Josephson Vortex States in Intermediate Fields

Motivated by recent resistance data in high $T_c$ superconductors in fields {\it parallel} to the CuO layers, we address two issues on the Josephson-vortex phase diagram, the appearances of structural transitions on the observed first order transition (FOT) curve in intermediate fields and of a lower critical point of the FOT line. It is found that some rotated pinned solids are more stable than the ordinary rhombic pinned solids with vacant interlayer spacings and that, due to the vertical portion in higher fields of the FOT line, the FOT tends to be destroyed by creating a lower critical point.Comment: 12 pages, 3 figures. To appear in J.Phys.Soc.Jpn. 71, No.2 (February, 2002

AKSZ-BV Formalism and Courant Algebroid-induced Topological Field Theories

We give a detailed exposition of the Alexandrov-Kontsevich-Schwarz- Zaboronsky superfield formalism using the language of graded manifolds. As a main illustarting example, to every Courant algebroid structure we associate canonically a three-dimensional topological sigma-model. Using the AKSZ formalism, we construct the Batalin-Vilkovisky master action for the model.Comment: 13 pages, based on lectures at Rencontres mathematiques de Glanon 200

Determination of Trace Levels of Uranium and Thorium in High Purity Gadolinium Sulfate Using ICP-MS with Solid-Phase Chromatographic Extraction Resin

The new Super-Kamiokande-Gadolinium (SK-Gd) project is an upgrade of the Super-Kamiokande (SK) detector. In the SK-Gd project, 0.2\% Gd$_2$(SO$_4$)$_3$ is loaded into the 50 kton water tank of the SK. One of the main purposes of the project is to discover Supernova Relic Neutrinos. Neutrino measurements and proton decay searches will also be performed in the SK-Gd. In order to measure solar neutrinos with a low energy threshold of $\sim$3.5 MeV in the SK-Gd, the main radioactive contaminations, $^{238}$U and $^{232}$Th, in Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O, should be minimized before loading. Our maximum levels for U and Th are 5 mBq (U)/kg (Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O) and 0.05 mBq (Th)/kg (Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O). In order to measure such low concentrations of U and Th in Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O, we developed the solid-phase extraction technique. Using this method, about 90\% or more U and Th could be efficiently extracted while Gd was reduced by a factor of about $10^{4}$. This allowed these radioactivity contaminations to be measured precisely as 0.04 mBq/kg (Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O) for U and 0.01 mBq/kg (Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O) for Th. We measured three pure Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O samples using this method and estimated that the purest one contained $<0.04$ mBq (U)/kg (Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O) and 0.06 $\pm$ 0.01 mBq (Th)/kg (Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O) by ICP-MS.Comment: 13 pages, 11 figure

Self-assembly of parallel atomic wires and periodic clusters of silicon on a vicinal Si(111) surface

Silicon self-assembly at step edges in the initial stage of homoepitaxial growth on a vicinal Si(111) surface is studied by scanning tunneling microscopy (STM). The resulting atomic structures change dramatically from a parallel array of 0.7 nm wide wires to one dimensionally aligned periodic clusters of the diameter ~ 2 nm and periodicity 2.7 nm in the very narrow range of growth temperatures between 400 and 300 C. These nanostructures are expected to play an important role in future development of silicon quantum computers. Mechanisms leading to such distinct structures are discussed.Comment: Accepted for publication in Phys. Rev. Lett. Numbers of pages and figures are 13 and 3, respectivel

Chemical potential jump between hole- and electron-doped sides of ambipolar high-Tc cuprate

In order to study an intrinsic chemical potential jump between the hole- and electron-doped high-Tc superconductors, we have performed core-level X-ray photoemission spectroscopy (XPS) measurements of Y0.38La0.62Ba1.74La0.26Cu3Oy (YLBLCO), into which one can dope both holes and electrons with maintaining the same crystal structure. Unlike the case between the hole-doped system La_2-xSrxCuO4 and the electron-doped system Nd_2-xCexCuO4, we have estimated the true chemical potential jump between the hole- and electron-doped YLBLCO to be ~0.8 eV, which is much smaller than the optical gaps of 1.4-1.7 eV reported for the parent insulating compounds. We attribute the reduced jump to the indirect nature of the charge-excitation gap as well as to the polaronic nature of the doped carriers.Comment: 4 pages, 3 figure

Universal Irreversibility of Normal Quantum Diffusion

Time-reversibility measured by the deviation of the perturbed time-reversed motion from the unperturbed one is examined for normal quantum diffusion exhibited by four classes of quantum maps with contrastive physical nature. Irrespective of the systems, there exist a universal minimal quantum threshold above which the system completely loses the past memory, and the time-reversed dynamics as well as the time-reversal characteristics asymptotically trace universal curves independent of the details of the systems.Comment: 4 pages, 4 figure

Evidence for realignment of the charge density wave state in ErTe3_3 and TmTe3_3 under uniaxial stress via elastocaloric and elastoresistivity measurements

We report the evolution of a charge density wave (CDW) state in the quasi-2D rare-earth tritellurides ($R$Te$_3$ for $R$=Er,Tm) as a function of in-plane uniaxial stress. Measurements of the elastocaloric effect, resistivity, and elastoresistivity allow us to demonstrate the importance of in-plane antisymmetric strain on the CDW and to establish a phase diagram. We show that modest tensile stress parallel to the in-plane $a$-axis can reversibly switch the direction of the ordering wavevector between the two in-plane directions. This work establishes $R$Te$_3$ as a promising model system for the study of strain-CDW interactions in a quasi-2D square lattice.Comment: 18 pages, 12 figure

Microscopic Study of Quantum Vortex-Glass Transition Field in Two-Dimensional Superconductors

The position of a field-tuned superconductor-insulator quantum transition occuring in disordered thin films is examined within the mean field approximation. Our calculation shows that the microscopic disorder-induced reduction of the quantum transition point found experimentally cannot be explained if the interplay between the disorder and an electron-electron repulsive interaction is ignored. This work is presented as a microscopic basis of an explanation (cond-mat/0105122) of resistive phenomena near the transition field.Comment: 16 pages, 5 figures. To appear in J.Phys.Soc.Jp