31,400 research outputs found

    Polarization Measurements and the Pairing Gap in the Universal Regime

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    We analyze recent cold-atom experiments on imbalanced Fermi systems using a minimal model with a BCS-like superfluid phase coexisting with a normal phase. This model is used to extract the T=0 pairing gap in the fully paired superfluid state. The recently measured particle density profiles are in good agreement with the theoretical predictions obtained from the universal parameters from previous Quantum Monte Carlo calculations. We find that the T=0 pairing gap is greater than 0.4 times the Fermi energy EFE_F, with a preferred value of 0.45±0.050.45 \pm 0.05 EFE_F. The ratio of the pairing gap Δ\Delta to the Fermi Energy EFE_F is larger here than in any other system of strongly-paired fermions in which individual pairs are unbound.Comment: 4 pages, 3 figures. Revised verison includes cosmetic changes to the text and figures. One reference adde

    Phase-field modelling of fracture in single crystal plasticity

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    We propose a phase-field model for ductile fracture in a single crystal within the kinematically linear regime, by combining the theory of single crystal plasticity as formulated in Gurtin et al. (2010) and the phase-field formulation for ductile fracture proposed by Ambati et al. (2015) . The model introduces coupling between plasticity and fracture through the dependency of the so-called degradation function from a scalar global measure of the accumulated plastic strain on all slip systems. A viscous regularization is introduced both in the treatment of plasticity and in the phase-field evolution equation. Testing of the model on two examples for face centred cubic single crystals indicates that fracture is predicted to initiate and develop in the regions of the maximum accumulated plastic strain, which is in agreement with phenomenological observations. A rotation of the crystallographic unit cell is shown to affect the test results in terms of failure pattern and corresponding global and local response

    DECOMPOSITION OF INCOME DISTRIBUTION AMONG FARM FAMILIES

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    The greater reliance of U.S. farm families on off-farm income has implications for the structure of agriculture and the distribution of income within agriculture. Using annual data on farm households from the Current Population Survey, the degree of income inequality for the U.S. and by region is assessed for 1984. The distribution of income among farm families is decomposed by income source. Off-farm income is shown to contribute to higher average incomes and reduce income inequality at the margin, but only in regions where full-time farming predominates. In the Northeast and South, increases in off-farm income increase regional income inequality.Consumer/Household Economics,

    Time Delay Induced Death in Coupled Limit Cycle Oscillators

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    We investigate the dynamical behaviour of two limit cycle oscillators that interact with each other via time delayed coupling and find that time delay can lead to amplitude death of the oscillators even if they have the same frequency. We demonstrate that this novel regime of amplitude "death" also exists for large collections of coupled identical oscillators and provide quantitative measures of this death region in the parameter space of coupling strength and time delay. Its implication for certain biological and physical applications is also pointed out.Comment: 4 aps formatted revtex pages; 3 figures; to be published in Phys. Rev. Let
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