2,695 research outputs found

    Lessons from a small country about the global obesity crisis

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    Developed countries had high obesity rates before the problem was taken seriously and hence the genesis must be seen in retrospect. Developing countries offer a clear view of causal factors but also opportunities for prevention, which must focus on both food and physical activity environments

    Lowest Order Constrained Variational Calculation of the Polarized Nuclear Matter with the Modern AV18AV_{18} Potential

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    The lowest order constrained variational method is applied to calculate the polarized symmetrical nuclear matter properties with the modern AV18AV_{18} potential performing microscopic calculations. Results based on the consideration of magnetic properties show no sign of phase transition to a ferromagnetic phase.Comment: 19 pages, 6 figure

    Polarized Neutron Matter: A Lowest Order Constrained Variational Approach

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    In this paper, we calculate some of the polarized neutron matter properties, using the lowest order constrained variational method with the AV18AV_{18} potential and employing a microscopic point of view. A comparison is also made between our results and those of other many-body techniques.Comment: 23 pages, 8 figure

    Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach

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    The relation between energy and density (known as the nuclear equation of state) plays a major role in a variety of nuclear and astrophysical systems. Spin and isospin asymmetries can have a dramatic impact on the equation of state and possibly alter its stability conditions. An example is the possible manifestation of ferromagnetic instabilities, which would indicate the existence, at a certain density, of a spin-polarized state with lower energy than the unpolarized one. This issue is being discussed extensively in the literature and the conclusions are presently very model dependent. We will report and discuss our recent progress in the study of spin-polarized neutron matter. The approach we take is microscopic and relativistic. The calculated neutron matter properties are derived from realistic nucleon-nucleon interactions. This makes it possible to understand the nature of the EOS properties in terms of specific features of the nuclear force model.Comment: 6 pages, 11 figures, revised/extended calculation

    Detectability of dissipative motion in quantum vacuum via superradiance

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    We propose an experiment for generating and detecting vacuum-induced dissipative motion. A high frequency mechanical resonator driven in resonance is expected to dissipate energy in quantum vacuum via photon emission. The photons are stored in a high quality electromagnetic cavity and detected through their interaction with ultracold alkali-metal atoms prepared in an inverted population of hyperfine states. Superradiant amplification of the generated photons results in a detectable radio-frequency signal temporally distinguishable from the expected background.Comment: 4 pages, 2 figure

    Anomalies in electrostatic calibrations for the measurement of the Casimir force in a sphere-plane geometry

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    We have performed precision electrostatic calibrations in the sphere-plane geometry and observed anomalous behavior. Namely, the scaling exponent of the electrostatic signal with distance was found to be smaller than expected on the basis of the pure Coulombian contribution and the residual potential found to be distance dependent. We argue that these findings affect the accuracy of the electrostatic calibrations and invite reanalysis of previous determinations of the Casimir force.Comment: 4 pages, 4 figure

    Thermal and dissipative effects in Casimir physics

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    We report on current efforts to detect the thermal and dissipative contributions to the Casimir force. For the thermal component, two experiments are in progress at Dartmouth and at the Institute Laue Langevin in Grenoble. The first experiment will seek to detect the Casimir force at the largest explorable distance using a cylinder-plane geometry which offers various advantages with respect to both sphere-plane and parallel-plane geometries. In the second experiment, the Casimir force in the parallel-plane configuration is measured with a dedicated torsional balance, up to 10 micrometers. Parallelism of large surfaces, critical in this configuration, is maintained through the use of inclinometer technology already implemented at Grenoble for the study of gravitationally bound states of ultracold neutrons, For the dissipative component of the Casimir force, we discuss detection techniques based upon the use of hyperfine spectroscopy of ultracold atoms and Rydberg atoms. Although quite challenging, this triad of experimental efforts, if successful, will give us a better knowledge of the interplay between quantum and thermal fluctuations of the electromagnetic field and of the nature of dissipation induced by the motion of objects in a quantum vacuum.Comment: Contribution to QFEXT'06, appeared in special issue of Journal of Physics
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