26,442 research outputs found

    Pion and Kaon Condensation at Finite Temperature and Density

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    In this paper, we study O(2N)-symmetric ϕ4\phi^4-theory at finite temperature and density using the 2PI-1/N expansion. As specific examples, we consider pion condensation at finite isospin chemical potential and kaon condensation at finite chemical potential for hyper charge and isospin charge. We calculate the phase diagrams and the quasiparticle masses for pions and kaons in the large-N limit. It is shown that the effective potential and the gap equation can be renormalized by using local counterterms for the coupling constant and mass parameter, which are independent of temperature and chemical potentials.Comment: 10 pages. 7 Figures. v2: Better plots and figs. Added significant number of refs v3: Accepted for publication in PRD. Added a figure and improved part on renormalization as well as presentatio

    Hybrid HVDC for supply of power to offshore oil platforms

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    A HVDC hybrid system, comprising a line commutated thyristor HVDC converter and a STATCOM, is proposed in this paper for supplying power to offshore oil platforms that do not have their own generation. The proposed system combines the robust performance, low capital cost and low power loss of a line commutated HVDC converter, with the fast dynamic performance of an equivalent VSC Transmission system. The paper describes the principles and control strategies of the proposed system. PSCAD/EMTDC simulations are presented to demonstrate the robust performance of the system using case studies of various operating conditions such as black-start, load perturbations, AC fault conditions and disturbance caused by the starting of large local induction machines

    Anisotropy study of multiferroicity in the pyroxene NaFeGe2_2O6_6

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    We present a study of the anisotropy of the dielectric, magnetic and magnetoelastic properties of the multiferroic clinopyroxene NaFeGe2_2O6_6. Pyroelectric currents, dielectric constants and magnetic susceptibilities as well as the thermal expansion and the magnetostriction were examined on large synthetic single crystals of NaFeGe2_2O6_6. The spontaneous electric polarization detected below TC11.6T_{\rm C}\simeq 11.6 K in an antiferromagnetically ordered state (TN13T_{\rm N}\simeq 13 K) is mainly lying within the acac plane with a small component along bb, indicating a triclinic symmetry of the multiferroic phase of NaFeGe2_2O6_6. The electric polarization can be strongly modified by applying magnetic fields along different directions. We derive detailed magnetic-field versus temperature phase diagrams and identify three multiferroic low-temperature phases, which are separated by a non-ferroelectric, antiferromagnetically ordered state from the paramagnetic high-temperature phase.Comment: 14 pages, 8 figures. (minor modifications and corrections of the text

    Observation of twin beam correlations and quadrature entanglement by frequency doubling in a two-port resonator

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    We demonstrate production of quantum correlated and entangled beams by second harmonic generation in a nonlinear resonator with two output ports. The output beams at wavelength 428.5 nm exhibit 0.9 dB of nonclassical intensity correlations and 0.3 dB of entanglement.Comment: 5 pages, 7 figure

    Feedback Enhanced Sensitivity in Optomechanics: Surpassing the Parametric Instability Barrier

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    The intracavity power, and hence sensitivity, of optomechanical sensors is commonly limited by parametric instability. Here we characterize the parametric instability induced sensitivity degradation in a micron scale cavity optomechanical system. Feedback via optomechanical transduction and electrical gradient force actuation is applied to suppress the parametric instability. As a result a 5.4 fold increase in mechanical motion transduction sensitivity is achieved to a final value of 1.9×1018mHz1/21.9\times 10^{-18}\rm m Hz^{-1/2}.Comment: 4 pages, 4 figure

    Use of ERTS data for a multidisciplinary analysis of Michigan resources

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    The author has identified the following significant results. The results of this investigation of ratioing simulated ERTS spectral bands and several non-ERTS bands (all collected by an airborne multispectral scanner) indicate that significant terrain information is available from band-ratio images. Ratio images, which are based on the relative spectral changes which occur from one band to another, are useful for enhancing differences and aiding the image interpreter in identifying and mapping the distribution of such terrain elements as seedling crops, all bare soil, organic soil, mineral soil, forest and woodlots, and marsh areas. In addition, the ratio technique may be useful for computer processing to obtain recognition images of large areas at lower costs than with statistical decision rules. The results of this study of ratio processing of aircraft MSS data will be useful for future processing and evaluation of ERTS-1 data for soil and landform studies. Additionally, the results of ratioing spectral bands other than those currently collected by ERTS-1 suggests that some other bands (particularly a thermal band) would be useful in future satellites

    The Stability Balloon for Two-dimensional Vortex Ripple Patterns

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    Patterns of vortex ripples form when a sand bed is subjected to an oscillatory fluid flow. Here we describe experiments on the response of regular vortex ripple patterns to sudden changes of the driving amplitude a or frequency f. A sufficient decrease of f leads to a "freezing" of the pattern, while a sufficient increase of f leads to a supercritical secondary "pearling" instability. Sufficient changes in the amplitude a lead to subcritical secondary "doubling" and "bulging" instabilities. Our findings are summarized in a "stability balloon" for vortex ripple pattern formation.Comment: 4 pages, 5 figure

    Squeezed state purification with linear optics and feed forward

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    A scheme for optimal and deterministic linear optical purification of mixed squeezed Gaussian states is proposed and experimentally demonstrated. The scheme requires only linear optical elements and homodyne detectors, and allows the balance between purification efficacy and squeezing degradation to be controlled. One particular choice of parameters gave a ten-fold reduction of the thermal noise with a corresponding squeezing degradation of only 11%. We prove optimality of the protocol, and show that it can be used to enhance the performance of quantum informational protocols such as dense coding and entanglement generation.Comment: 4 pages, 3 figure

    Andreev states near short-ranged pairing potential impurities

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    We study Andreev states near atomic scale modulations in the pairing potential in both ss- and d-wave superconductors with short coherence lengths. For a moderate reduction of the local gap, the states exist only close to the gap edge. If one allows for local sign changes of the order parameter, however, resonances can occur at energies close to the Fermi level. The local density of states (LDOS) around such pairing potential defects strongly resembles the patterns observed by tunneling measurements around Zn impurities in Bi2_2Sr2_2CaCu2_2O8+x_{8+x} (BSCCO). We discuss how this phase impurity model of the Zn LDOS pattern can be distinguished from other proposals experimentally.Comment: 4 pages, 4 figure

    Creative Business in Australia Learnings from the Creative Industries Innovation Centre, 2009 To 2015

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    As the largest ever Australian government investment in creative industries development, the Creative Industries Innovation Centre delivered tailored business services to more than 1500 creative businesses from 2009 to 2015 and provided industry intelligence and advice for public policy and peak sectoral activity. This collection gives an overview of the current ‘state of business’ in Australia’s creative industries – both as an industry sector in its own right and as an enabling sector and skills set for other industries – and reflects on business needs, creative industries policy and support services for the sector. With contributions from the Centre’s team of senior business advisers and from leading Australian researchers who worked closely with the Centre –including experts on design-led innovation and the creative economy – and case studies of leading Australia creative businesses, the book is intended as and industry-relevant contribution to business development and public policy
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