3,439 research outputs found

    Reduction of Dilute Ising Spin Glasses

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    The recently proposed reduction method for diluted spin glasses is investigated in depth. In particular, the Edwards-Anderson model with \pm J and Gaussian bond disorder on hyper-cubic lattices in d=2, 3, and 4 is studied for a range of bond dilutions. The results demonstrate the effectiveness of using bond dilution to elucidate low-temperature properties of Ising spin glasses, and provide a starting point to enhance the methods used in reduction. Based on that, a greedy heuristic call ``Dominant Bond Reduction'' is introduced and explored.Comment: 10 pages, revtex, final version, find related material at http://www.physics.emory.edu/faculty/boettcher

    Stability of the replica-symmetric saddle-point in general mean-field spin-glass models

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    Within the replica approach to mean-field spin-glasses the transition from ergodic high-temperature behaviour to the glassy low-temperature phase is marked by the instability of the replica-symmetric saddle-point. For general spin-glass models with non-Gaussian field distributions the corresponding Hessian is a 2n×2n2^n\times 2^n matrix with the number nn of replicas tending to zero eventually. We block-diagonalize this Hessian matrix using representation theory of the permutation group and identify the blocks related to the spin-glass susceptibility. Performing the limit n0n\to 0 within these blocks we derive expressions for the de~Almeida-Thouless line of general spin-glass models. Specifying these expressions to the cases of the Sherrington-Kirkpatrick, Viana-Bray, and the L\'evy spin glass respectively we obtain results in agreement with previous findings using the cavity approach

    First IBEX observations of the terrestrial plasma sheet and a possible disconnection event

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    The Interstellar Boundary Explorer (IBEX) mission has recently provided the first all-sky maps of energetic neutral atoms (ENAs) emitted from the edge of the heliosphere as well as the first observations of ENAs from the Moon and from the magnetosheath stagnation region at the nose of the magnetosphere. This study provides the first IBEX images of the ENA emissions from the nightside magnetosphere and plasma sheet. We show images from two IBEX orbits: one that displays typical plasma sheet emissions, which correlate reasonably well with a model magnetic field, and a second that shows a significant intensification that may indicate a near-Earth (similar to 10 R(E) behind the Earth) disconnection event. IBEX observations from similar to 0.5-6 keV indicate the simultaneous addition of both a hot (several keV) and colder (similar to 700 eV) component during the intensification; if IBEX directly observed magnetic reconnection in the magnetotail, the hot component may signify the plasma energization

    Limits on the HI content of the dwarf galaxy Hydra II

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    Sensitive 21cm HI observations have been made with the Green Bank Telescope toward the newly-discovered Local Group dwarf galaxy Hydra II, which may lie within the leading arm of the Magellanic Stream. No neutral hydrogen was detected. Our 5-sigma limit of MHI < 210 solar masses for a 15 km/s linewidth gives a gas-to-luminosity ratio MHI/L_V < 2.6 x 10^{-2} Mo / Lo. The limits on HI mass and MHI/L_V are typical of dwarf galaxies found within a few hundred kpc of the Milky Way. Whatever the origin of Hydra II, its neutral gas properties are not unusual.Comment: Accepted for publication in Astronomy & Astrophysic

    The phase diagram of L\'evy spin glasses

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    We study the L\'evy spin-glass model with the replica and the cavity method. In this model each spin interacts through a finite number of strong bonds and an infinite number of weak bonds. This hybrid behaviour of L\'evy spin glasses becomes transparent in our solution: the local field contains a part propagating along a backbone of strong bonds and a Gaussian noise term due to weak bonds. Our method allows to determine the complete replica symmetric phase diagram, the replica symmetry breaking line and the entropy. The results are compared with simulations and previous calculations using a Gaussian ansatz for the distribution of fields.Comment: 20 pages, 7 figure

    THE IMPACT OF BANK-SPECIFIC FACTORS ON NON-PERFORMING LOAN IN INDONESIA: EVIDENCE FROM ARDL MODEL APPROACH

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    Non-performing Loan (NPL) is an indicator that is generally used to determine the ability of bank management to manage non-performing loans. This study aims to analyze the impact of bank-specific factors on NPL. The bank-specific factors are Capital Adequacy Ratio (CAR), Return on Assets (ROA), Operating Expenses on Operating Income (BOPO), and Loan to Deposit Ratio (LDR). The data used is monthly time series data, a case study on Commercial Banks in Indonesia from January 2015 to August 2020. The model used to analyze these problems is Autoregressive Distributed Lag (ARDL). The results obtained are ARDL(1,6,0,1,1) model is the best model. The model shows that bank-specific factors have a direct impact on NPL. Specifically, the ARDL bounds test offers the analysis results, which show that the ability of bank-specific factors to explain the NPL of commercial banks in Indonesia is 84%. At the same time, 16% are other factors outside the model. The analysis results show a long-run cointegration relationship between NPL and specific characteristics, CAR, ROA, and BOPO. Then, only CAR, BOPO, and LDR impact NPL in the short-run relationship. The equilibrium correction obtained is significant and confirms a long-run relationship. The equilibrium correction indicates a high velocity towards stability after a shock. It means that the performance of Commercial Banks in Indonesia is outstanding during the COVID-19 Pandemic because the ability to recover from shock is relatively faste
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