177 resultados para FLUCTUATION RELATIONS

em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast


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We report the experimental reconstruction of the nonequilibrium work probability distribution in a closed quantum system, and the study of the corresponding quantum fluctuation relations. The experiment uses a liquid-state nuclear magnetic resonance platform that offers full control on the preparation and dynamics of the system. Our endeavors enable the characterization of the out-of-equilibrium dynamics of a quantum spin from a finite-time thermodynamics viewpoint.

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We study the statistics of the work done, the fluctuation relations and the irreversible entropy production in a quantum many-body system subject to the sudden quench of a control parameter. By treating the quench as a thermodynamic transformation we show that the emergence of irreversibility in the nonequilibrium dynamics of closed many-body quantum systems can be accurately characterized. We demonstrate our ideas by considering a transverse quantum Ising model that is taken out of equilibrium by the instantaneous switching of the transverse field.

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Using the operational framework of completely positive, trace preserving operations and thermodynamic fluctuation relations, we derive a lower bound for the heat exchange in a Landauer erasure process on a quantum system. Our bound comes from a nonphenomenological derivation of the Landauer principle which holds for generic nonequilibrium dynamics. Furthermore, the bound depends on the nonunitality of dynamics, giving it a physical significance that differs from other derivations. We apply our framework to the model of a spin-1/2 system coupled to an interacting spin chain at finite temperature.

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This article uses attitudinal data to explore Catholic and Protestant perspectives on community relations and equality since the paramilitary cease fires in 1994. Although attitudes tend to fluctuate with the‘headline grabbing'events of the day, the article argues that there are signs that some fundamental changes have taken place in the post cease fire period. Of particular importance in this regard is the positive response recorded by the Catholic community towards government measures to tackle disadvantage and inequality. Equally significant is the protestant response to many of these measures which is often one of ambivalence rather than derision. In so far as the data appear to challenge the‘zero-sum'game that traditionally underpins relations between the two communities in Northern Ireland, they provide some grounds for optimism. Yet such optimism is tempered somewhat by the seeds of discontent which are manifest within the protestant community, particularly around issues of equality in employment and cultural traditions. Despite the more positive assessment of community relations and equality in 2002, it is argued that further monitoring will be required to determine the long-term effects of policy reform on relationships between the two communit

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This article provides an account of practice-based research of, at least, one-star quality in terms of its contribution to both theory and practice. Aimed at practitioner (as opposed to academic) psychologists, the article addresses a dimension of the practitioner role that has remained silent in the literature. The article makes creative and original connections between school effectiveness, school improvement and education in a divided society. Post 11th September, the article was described as being highly original, significant and relevant to all practising educational psychologists. Concrete evidence for this is gained from, eg: hits on the online electronic version (2002-2003 Annual Report of the Association of Educational Psychologists), citations in reviews of research, and author invitations to present his work at UK and international practitioner psychology conferences. The article is published in the premier journal reporting on quality applied educational research and practice within the United Kingdom and beyond.