7,732 research outputs found

    Superconductivity Near a Quantum Critical Point in Ba(Fe,Co)2As2

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    We will examine the possible link between spin fluctuations and the superconducting mechanism in the iron-based high temperature superconductor Ba(Fe,Co)2As2 based on NMR and high pressure transport measurements.Comment: Invited paper to m2s-IX (2009

    Momentum Distribution for Bosons with Positive Scattering Length in a Trap

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    The coordinate-momentum double distribution function ρ(r,p)d3rd3p\rho ({\bf r}, {\bf p}) d^{3}rd^{3}p is calculated in the local density approximation for bosons with positive scattering length aa in a trap. The calculation is valid to the first order of aa. To clarify the meaning of the result, it is compared for a special case with the double distribution function ρwd3rd3p\rho_{w}d^{3} rd^{3}p of Wigner.Comment: Latex fil

    NMR Search for the Spin Nematic State in LaFeAsO Single Crystal

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    We report a 75-As single crystal NMR investigation of LaFeAsO, the parent phase of a pnictide high Tc superconductor. We demonstrate that spin dynamics develop a strong two-fold anisotropy within each orthorhombic domain below the tetragonal-orthorhombic structural phase transition at T[TO]~156 K. This intermediate state with a dynamical breaking of the rotational symmetry freezes progressively into a spin density wave (SDW) below T[SDW]~142 K. Our findings are consistent with the presence of a spin nematic state below T[TO] with an incipient magnetic order.Comment: Revised manuscript accepted for publication in Phys. Rev. Let

    Analysis of pion elliptic flows and HBT interferometry in a granular quark-gluon plasma droplet model

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    In many simulations of high-energy heavy-ion collisions on an event-by-event analysis, it is known that the initial energy density distribution in the transverse plane is highly fluctuating. Subsequent longitudinal expansion will lead to many longitudinal tubes of quark-gluon plasma which have tendencies to break up into many spherical droplets because of sausage instabilities. We are therefore motivated to use a model of quark-gluon plasma granular droplets that evolve hydrodynamically to investigate pion elliptic flows and Hanbury-Brown-Twiss interferometry. We find that the data of pion transverse momentum spectra, elliptic flows, and HBT radii in \sqrt{s_{NN}}=200 GeV Au + Au collisions at RHIC can be described well by an expanding source of granular droplets with an anisotropic velocity distribution.Comment: 9 pages, 6 figures, in Late

    Bose-Einstein Condensation of Atoms in a Trap

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    We point out that the local density approximation (LDA) of Oliva is an adaptation of the Thomas-Fermi method, and is a good approximation when ε=ω/kT0\varepsilon = \hbar\omega/kT 0, the LDA leads to a quantitative result (14') easily checked by experiments. Critical remarks are made about the physics of the many body problem in terms of the scattering length aa.Comment: 9 pages, latex. one figure, available from author

    More on volume dependence of spectral weight function

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    Spectral weight functions are easily obtained from two-point correlation functions and they might be used to distinguish single-particle from multi-particle states in a finite-volume lattice calculation, a problem crucial for many lattice QCD simulations. In previous studies, it is shown that the spectral weight function for a broad resonance shares the typical volume dependence of a two-particle scattering state i.e. proportional to 1/L31/L^3 in a large cubic box of size LL while the narrow resonance case requires further investigation. In this paper, a generalized formula is found for the spectral weight function which incorporates both narrow and broad resonance cases. Within L\"uscher's formalism, it is shown that the volume dependence of the spectral weight function exhibits a single-particle behavior for a extremely narrow resonance and a two-particle behavior for a broad resonance. The corresponding formulas for both A1+A^+_1 and T1T^-_1 channels are derived. The potential application of these formulas in the extraction of resonance parameters are also discussed

    Monolithic Si bolometer array for the Caltech Submillimeter Observatory

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    We are developing a submillimeter continuum camera for the Caltech Submillimeter Observatory (CSO) located on Mauna Kea. The camera will employ a monolithic Si bolometer array which was developed by Mosley et al. at the NASA Goddard Space Flight Center (GSFC). The camera will be cooled to a temperature of about 300 mK in a ^3He cryostat, and will operate primarily at wavelengths of 350 and 450 micrometers. We plan to use a bolometer array with 1 x 24 directly illuminated pixels, each pixel of dimension 1 x 2 mm^2, which is about half of the F/4 beam size at these wavelengths. Each pixel is 10 - 12 micrometers thick and is supported only by four thin Si legs formed by wet chemical etch. The pixels are doped n-type by phosphorus implantation, compensated by boron implantation. Signals from the bolometer pixels are first amplified by cryogenically cooled FETs. The signals are further amplified by room-temperature amplifiers and then separately digitized by 16 bit A/D converters with differential inputs. The outputs of the A/D converters are fed into a digital signal processing board via fiber-optic cables. The electronics and data acquisition system were designed by the Goddard group. We will report the status of this effort

    Strategi Incumbent Parpol Mempertahankan Suara Pasca Pindah Partai pada Pemilu Legislatif Kota Denpasar Tahun 2014

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    Incumbent Political Party Strategies Maintaining the Voters after Moving Political Parties In the legislative elections with a case study AANG Widiada reelected Post Moving from the Golkar Party to Nasdem as legislators Denpasar period 2014-2019. This research has been done in north Denpasar District. This research using qualitative method with descriptive type of analysis. Primary data was collected through interview technique purposive sampling and snowball sampling. Secondary Data obtained from news articles, the Internet, and books related to the study. The study refers to offensive and defensive strategies by Peter Schroder. The findings research is the offensive strategy implemented through Political Socialization Program and Performance Dharma Discourse at Pura Desa in Peguyangan village. Defensive strategies implemented through a mass ceremony of Memukur and Mesangih ceremony in Puri Peguyangan. Both of these strategies are winning strategies to pass the legislative elections in north Denpasar election area for the period 2014-2019
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