2,412 research outputs found

    Non-equilibrium Relations for Spin Glasses with Gauge Symmetry

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    We study the applications of non-equilibrium relations such as the Jarzynski equality and fluctuation theorem to spin glasses with gauge symmetry. It is shown that the exponentiated free-energy difference appearing in the Jarzynski equality reduces to a simple analytic function written explicitly in terms of the initial and final temperatures if the temperature satisfies a certain condition related to gauge symmetry. This result is used to derive a lower bound on the work done during the non-equilibrium process of temperature change. We also prove identities relating equilibrium and non-equilibrium quantities. These identities suggest a method to evaluate equilibrium quantities from non-equilibrium computations, which may be useful to avoid the problem of slow relaxation in spin glasses.Comment: 8 pages, 2 figures, submitted to JPS

    Medical Tourism in Barbados: Negotiating Inherent Tensions

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    This chapter draws on our long term-research program examining medical tourism in Barbados and the wider Anglophone Caribbean. Since 2011 we have undertaken 69 semi-structured interviews and three focus groups with a wide range of health system and tourism sector stakeholders in Barbados, compiled a comprehensive collection of state and media reports discussing medical tourism, and collectively spent over a year conducting on-site ethnographic fieldwork that has included many informal conversations with users of the Barbadian health system from a wide range of backgrounds. Together, these datasets and experiences provide a rich understanding of the potential considerations and hopes arising from the ongoing discussion about medical tourism development in a small island setting. Exploring these considerations and hopes suggests ways in which Barbados and other small island states seeking to develop their medical tourism sectors can negotiate a structure for medical tourism that can best meet their development goals

    Quantum Operation Time Reversal

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    The dynamics of an open quantum system can be described by a quantum operation, a linear, complete positive map of operators. Here, I exhibit a compact expression for the time reversal of a quantum operation, which is closely analogous to the time reversal of a classical Markov transition matrix. Since open quantum dynamics are stochastic, and not, in general, deterministic, the time reversal is not, in general, an inversion of the dynamics. Rather, the system relaxes towards equilibrium in both the forward and reverse time directions. The probability of a quantum trajectory and the conjugate, time reversed trajectory are related by the heat exchanged with the environment.Comment: 4 page

    Agmatine and Agmatine Analogs in the Treatment of Epilepsy, Seizure, and Electroconvulsive Disorders

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    Pharmaceutical preparations containing of agmatine, congeners, analogs or derivatives thereof for use in preventing or treating epilepsy, seizures and other electroconvulsive disorders are provided. Embodiments include administering an effective amount of agmatine, an agmatine analog or a pharmaceutically acceptable salt thereof to a human subject in need of treatment or prevention of epilepsy, seizure or other electroconvulsive disorder to treat, reduce, or prevent the disorder in the subject

    Nonequilibrium work on spin glasses in longitudinal and transverse fields

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    We derive a number of exact relations between equilibrium and nonequilibrium quantities for spin glasses in external fields using the Jarzynski equality and gauge symmetry. For randomly-distributed longitudinal fields, a lower bound is established for the work done on the system in nonequilibrium processes, and identities are proven to relate equilibrium and nonequilibrium quantities. In the case of uniform transverse fields, identities are proven between physical quantities and exponentiated work done to the system at different parts of the phase diagram with the context of quantum annealing in mind. Additional relations are given, which relate the exponentiated work in quantum and simulated (classical) annealing. It is also suggested that the Jarzynski equality may serve as a guide to develop a method to perform quantum annealing under non-adiabatic conditions.Comment: 17 pages, 5 figures, submitted to JPS

    Apparatus for dimensional characterization of fused silica fibers for the suspensions of advanced gravitational wave detectors

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    Detection of gravitational waves from astrophysical sources remains one of the most challenging problems faced by experimental physicists. A significant limit to the sensitivity of future long-baseline interferometric gravitational wave detectors is thermal displacement noise of the test mass mirrors and their suspensions. Suspension thermal noise results from mechanical dissipation in the fused silica suspension fibers suspending the test mass mirrors and is therefore an important noise source at operating frequencies between ∼10 and 30 Hz. This dissipation occurs due to a combination of thermoelastic damping, surface and bulk losses. Its effects can be reduced by optimizing the thermoelastic and surface loss, and these parameters are a function of the cross sectional dimensions of the fiber along its length. This paper presents a new apparatus capable of high resolution measurements of the cross sectional dimensions of suspension fibers of both rectangular and circular cross section, suitable for use in advanced detector mirror suspensions

    Extended Clausius Relation and Entropy for Nonequilibrium Steady States in Heat Conducting Quantum Systems

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    Recently, in their attempt to construct steady state thermodynamics (SST), Komatsu, Nakagwa, Sasa, and Tasaki found an extension of the Clausius relation to nonequilibrium steady states in classical stochastic processes. Here we derive a quantum mechanical version of the extended Clausius relation. We consider a small system of interest attached to large systems which play the role of heat baths. By only using the genuine quantum dynamics, we realize a heat conducting nonequilibrium steady state in the small system. We study the response of the steady state when the parameters of the system are changed abruptly, and show that the extended Clausius relation, in which "heat" is replaced by the "excess heat", is valid when the temperature difference is small. Moreover we show that the entropy that appears in the relation is similar to von Neumann entropy but has an extra symmetrization with respect to time-reversal. We believe that the present work opens a new possibility in the study of nonequilibrium phenomena in quantum systems, and also confirms the robustness of the approach by Komtatsu et al.Comment: 19 pages, 2 figure

    Literacy Assessment New Zealand Style

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    It\u27s mostly performance based. It assesses students in teams as well as individually. What\u27s more, students like it

    Density fluctuations and the structure of a nonuniform hard sphere fluid

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    We derive an exact equation for density changes induced by a general external field that corrects the hydrostatic approximation where the local value of the field is adsorbed into a modified chemical potential. Using linear response theory to relate density changes self-consistently in different regions of space, we arrive at an integral equation for a hard sphere fluid that is exact in the limit of a slowly varying field or at low density and reduces to the accurate Percus-Yevick equation for a hard core field. This and related equations give accurate results for a wide variety of fields
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