Search results for "Stati"

Comparative theoretical study of the Ag–MgO (100) and (110) interfaces

1999

We have calculated the atomic and electronic structures of Ag–MgO(100) and (110) interfaces using a periodic (slab) model and an ab initio Hartree–Fock approach with a posteriori electron correlation corrections. The electronic structure information includes interatomic bond populations, effective charges, and multipole moments of ions. This information is analyzed in conjunction with the interface binding energy and the equilibrium distances for both interfaces for various coverages. There are significant differences between partly covered surfaces and surfaces with several layers of metal, and these can be understood in terms of electrostatics and the electron density changes. For complet…

(H,ρ)-induced dynamics and large time behaviors

2018

In some recent papers, the so called (H,ρ)-induced dynamics of a system S whose time evolution is deduced adopting an operatorial approach, borrowed in part from quantum mechanics, has been introduced. Here, H is the Hamiltonian for S, while ρ is a certain rule applied periodically (or not) on S. The analysis carried on throughout this paper shows that, replacing the Heisenberg dynamics with the (H,ρ)-induced one, we obtain a simple, and somehow natural, way to prove that some relevant dynamical variables of S may converge, for large t, to certain asymptotic values. This cannot be so, for finite dimensional systems, if no rule is considered. In this case, in fact, any Heisenberg dynamics im…

Remnants of Anderson localization in prethermalization induced by white noise

2017

We study the non-equilibrium evolution of a one-dimensional quantum Ising chain with spatially disordered, time-dependent, transverse fields characterised by white noise correlation dynamics. We establish pre-thermalization in this model, showing that the quench dynamics of the on-site transverse magnetisation first approaches a metastable state unaffected by noise fluctuations, and then relaxes exponentially fast towards an infinite temperature state as a result of the noise. We also consider energy transport in the model, starting from an inhomogeneous state with two domain walls which separate regions characterised by spins with opposite transverse magnetization. We observe at intermedia…

Reinforcement learning approach to nonequilibrium quantum thermodynamics

2021

We use a reinforcement learning approach to reduce entropy production in a closed quantum system brought out of equilibrium. Our strategy makes use of an external control Hamiltonian and a policy gradient technique. Our approach bears no dependence on the quantitative tool chosen to characterize the degree of thermodynamic irreversibility induced by the dynamical process being considered, require little knowledge of the dynamics itself and does not need the tracking of the quantum state of the system during the evolution, thus embodying an experimentally non-demanding approach to the control of non-equilibrium quantum thermodynamics. We successfully apply our methods to the case of single- …

Entanglement entropy in a periodically driven quantum Ising chain

2016

We numerically study the dynamics of entanglement entropy, induced by an oscillating time periodic driving of the transverse field, h(t), of a one-dimensional quantum Ising chain. We consider several realizations of h(t), and we find a number of results in analogy with entanglement entropy dynamics induced by a sudden quantum quench. After short-time relaxation, the dynamics of entanglement entropy synchronises with h(t), displaying an oscillatory behaviour at the frequency of the driving. Synchronisation in the dynamics of entanglement entropy, is spoiled by the appearance of quasi-revivals which fade out in the thermodynamic limit, and which we interpret using a quasi-particle picture ada…

Validación del Autoconcepto Forma 5 en Universitarios Peruanos: Una Herramienta para la Psicología Positiva

2015

ResumenEl autoconcepto, aunque central en la psicología tradicional, ha cobrado importancia recientemente en el contexto de la psicología positiva. El Autoconcepto Forma 5 (AF5) es una medida muy utilizada en el contexto hispanohablante. Sin embargo, no existen estudios sobre sus propiedades psicométricas más allá de la fiabilidad en población peruana. El objetivo es presentar las propiedades psicométricas de la escala multidimensional AF5 en universitarios peruanos. Se recogió una muestra de 527 estudiantes universitarios. La encuesta incluyó, además del AF5, medidas de esperanza disposicional y satisfacción con la vida. Se llevó a cabo un análisis factorial confirmatorio para evaluar la v…

The transition state and cognate concepts

2019

Abstract This review aims firstly to clarify the meanings of key terms and concepts associated with the idea of the transition state, as developed by theoreticians and applied by experimentalist, and secondly to provide an update to the meaning and significance of the transition state in an era when computational simulation, in which complexity is being increasingly incorporated, is commonly employed as a means by which to bridge the realms of theory and experiment. The relationship between the transition state and the potential-energy surface for an elementary reaction is explored, with discussion of the following terms: saddle point, minimum-energy reaction path, reaction coordinate, acti…

A singular (p,q)-equation with convection and a locally defined perturbation

2021

Abstract We consider a parametric Dirichlet problem driven by the ( p , q ) -Laplacian and a reaction which is gradient dependent (convection) and the competing effects of two more terms, one a parametric singular term and a locally defined perturbation. We show that for all small values of the parameter the problem has a positive smooth solution.

Characteristic asymptotics for fast chemical reaction

1995

A note on Jordan’s inequality

2020

Abstract In this paper we obtain some bounds in terms of polynomials for the function sin x x {{\sin x} \over x} , x ∈ [0, π].