Fluctuation relations for systems in constant magnetic field

The validity of the Fluctuation Relations (FR) for systems in a constant magnetic field is investigated. Recently introduced time-reversal symmetries that hold in presence of static electric and magnetic fields and of deterministic thermostats are used to prove the transient FR without invoking, as commonly done, inversion of the magnetic field. Steady-state FR are also derived, under the t-mixing condition. These results extend the predictive power of important statistical mechanics relations. We illustrate this via the non-linear response for the cumulants of the dissipation, showing how the new FR enable to determine analytically null cumulants also for systems in a single magnetic field.Comment: 1 figure, added reference

Analysis of the quantum-classical Liouville equation in the mapping basis

The quantum-classical Liouville equation provides a description of the dynamics of a quantum subsystem coupled to a classical environment. Representing this equation in the mapping basis leads to a continuous description of discrete quantum states of the subsystem and may provide an alternate route to the construction of simulation schemes. In the mapping basis the quantum-classical Liouville equation consists of a Poisson bracket contribution and a more complex term. By transforming the evolution equation, term-by-term, back to the subsystem basis, the complex term (excess coupling term) is identified as being due to a fraction of the back reaction of the quantum subsystem on its environment. A simple approximation to quantum-classical Liouville dynamics in the mapping basis is obtained by retaining only the Poisson bracket contribution. This approximate mapping form of the quantum-classical Liouville equation can be simulated easily by Newtonian trajectories. We provide an analysis of the effects of neglecting the presence of the excess coupling term on the expectation values of various types of observables. Calculations are carried out on nonadiabatic population and quantum coherence dynamics for curve crossing models. For these observables, the effects of the excess coupling term enter indirectly in the computation and good estimates are obtained with the simplified propagation

Spazio Europeo della Ricerca, Strategia di Lisbona e il 7° Programma Quadro

Invited Submission

Approximating Time-Dependent Quantum Statistical Properties

Computing quantum dynamics in condensed matter systems is an open challenge due to the exponential scaling of exact algorithms with the number of degrees of freedom. Current methods try to reduce the cost of the calculation using classical dynamics as the key ingredient of approximations of the quantum time evolution. Two main approaches exist, quantum classical and semi-classical, but they suffer from various difficulties, in particular when trying to go beyond the classical approximation. It may then be useful to reconsider the problem focusing on statistical time-dependent averages rather than directly on the dynamics. In this paper, we discuss a recently developed scheme for calculating symmetrized correlation functions. In this scheme, the full (complex time) evolution is broken into segments alternating thermal and real-time propagation, and the latter is reduced to classical dynamics via a linearization approximation. Increasing the number of segments systematically improves the result with respect to full classical dynamics, but at a cost which is still prohibitive. If only one segment is considered, a cumulant expansion can be used to obtain a computationally efficient algorithm, which has proven accurate for condensed phase systems in moderately quantum regimes. This scheme is summarized in the second part of the paper. We conclude by outlining how the cumulant expansion formally provides a way to improve convergence also for more than one segment. Future work will focus on testing the numerical performance of this extension and, more importantly, on investigating the limit for the number of segments that goes to infinity of the approximate expression for the symmetrized correlation function to assess formally its convergence to the exact result

Doctor of Philosophy

dissertationIn the recent past, the mental health system has responded to calls for deinstitutionalization and has had to deal with steadily decreasing flows of money. At the same time, a growing number of people who need treatment are finding themselves in the criminal justice system. The criminal justice system frequently finds it has to care for mentally ill individuals even though that is not their mission. In order to better address the needs of mentally ill individuals in both systems they have had to collaborate on behalf of those they serve. This study set out to explore the possibility of inherent problems in the way mental health and criminal justice professionals viewed each other, perceived barriers to collaboration, and possible inroads to better collaboration. Using a qualitative methodology based on the constructivist paradigm and systems theory, fourteen mental health and 15 criminal justice professionals were interviewed. Semistructured questionnaires in separate focus groups were used to explore their perceptions of each other, each other‘s systems, and barriers that individuals with mental illnesses in those systems face. The results indicated that mental health and criminal justice professionals‘ views varied according to their education, experiences with each other, and proximity of working with each other. The results also indicated that funding problems, low cross system education, service gaps, and inconsistency in professionalism inhibited collaboration between the two systems. Participants felt education regarding each system‘s philosophies, appropriately shared responsibilities, and understanding the limits both systems would help eliminate some barriers faced in collaboration. Participants said benefits of close collaboration would include higher success rates for mentally ill individuals, less recidivism in both systems, and increased professional satisfaction. Implications of the study indicated the need for increased education in both systems regarding the purpose, function, and philosophies of both systems. Also, leaders and front line professionals should focus on making their interactions with each other more consistent, clear, and available. Further research should investigate quantitative verification of the results, policy implementation to promote collaborative efforts, and educational efforts to improve the perceptions of mental health and criminal justice professionals of each other

ESL students\u27 perceptions of role-play activities

There has been significant discussion on the use of role-play activities. Proponents of role-play believe that the activity provides learners with opportunities to communicate freely and spontaneously in different situations. However, researchers have also identified issues that may jeopardize the effectiveness of role-plays. Despite the debate, few studies have focused on the students\u27 point of view. The current qualitative study investigated ESL students\u27 perceptions of role-play activities drawing on observations, questionnaires, and interviews. The results showed that the participants recognized several benefits (e.g., improving oral proficiency, acquiring vocabulary, and rehearsing for real-life communication) while also acknowledging some limitations such as artificiality and lack of vocabulary and ideas

Fluctuation relations for dissipative systems in constant external magnetic field: Theory and molecular dynamics simulations

We illustrate how, contrary to common belief, transient Fluctuation Relations (FRs) for systems in constant external magnetic field hold without the inversion of the field. Building on previous work providing generalized time-reversal symmetries for systems in parallel external magnetic and electric fields, we observe that the standard proof of these important nonequilibrium properties can be fully reinstated in the presence of net dissipation. This generalizes recent results for the FRs in orthogonal fields-an interesting but less commonly investigated geometry-and enables direct comparison with existing literature. We also present for the first time a numerical demonstration of the validity of the transient FRs with nonzero magnetic field via nonequilibrium molecular dynamics simulations of a realistic model of liquid NaCl

Misfortune caused by death, personal identity and what matters in survival

This article presents and discusses concepts and arguments found in debates on three philosophical problems: the misfortune inflicted by death on the person who dies; personal identity; and what is important in survival. First, it outlines the debate raised in the argument by Epicurus, to whom death means nothing to those who die. Second, the rivalry between neo-Lockeans and animalists regarding the most plausible criterion of personal identity is presented and discussed. Finally, a discussion on whether the misfortune caused by death is or not related to personal identity is conducted. The paper concludes that the dimension of the misfortune caused by death depends on both the amount of goods one is deprived of by death and on the interest such an individual would have to continue living. The aforementioned philosophical problems make up a core of acute issues such as decisions regarding the maintenance of life and delaying death.Este artigo apresenta e discute conceitos e argumentos encontrados em debates sobre três problemas filosóficos: o infortúnio infligido pela morte a quem morre; identidade pessoal; e o que é importante para a sobrevivência. Em primeiro lugar, delineia o debate suscitado no argumento de Epicuro, para quem a morte nada significa para os que morrem. Em segundo lugar, é apresentada e discutida a rivalidade entre neo-lockeanos e animalistas em relação ao critério mais plausível de identidade pessoal. Por fim, é feita uma discussão sobre se o infortúnio causado pela morte está ou não relacionado à identidade pessoal. O artigo conclui que a dimensão do infortúnio causado pela morte depende tanto da quantidade de bens de que se é privado pela morte quanto do interesse que tal indivíduo teria de continuar vivendo. Os problemas filosóficos mencionados constituem um núcleo de questões agudas, como as decisões a respeito da manutenção da vida e do adiamento da morte

Fluctuation relations for systems in a constant magnetic field

The validity of the fluctuation relations (FRs) for systems in a constant magnetic field is investigated. Recently introduced time-reversal symmetries that hold in the presence of static electric and magnetic fields and of deterministic thermostats are used to prove the transient FRs without invoking, as commonly done, inversion of the magnetic field. Steady-state FRs are also derived, under the t-mixing condition. These results extend the predictive power of important statistical mechanics relations. We illustrate this via the nonlinear response for the cumulants of the dissipation, showing how the alternative FRs enable one to determine analytically null cumulants also for systems in a single magnetic field