Search results for " METODI"

On quantumness in multi-parameter quantum estimation

2019

In this article we derive a measure of quantumness in quantum multi-parameter estimation problems. We can show that the ratio between the mean Uhlmann Curvature and the Fisher Information provides a figure of merit which estimates the amount of incompatibility arising from the quantum nature of the underlying physical system. This ratio accounts for the discrepancy between the attainable precision in the simultaneous estimation of multiple parameters and the precision predicted by the Cram\'er-Rao bound. As a testbed for this concept, we consider a quantum many-body system in thermal equilibrium, and explore the quantum compatibility of the model across its phase diagram.

Spectral characteristics of steady-state Lévy flights in confinement potential profiles

2016

The steady-state correlation characteristics of superdiffusion in the form of Levy flights in one-dimensional confinement potential profiles are investigated both theoretically and numerically. Specifically, for Cauchy stable noise we calculate the steady-state probability density function for an infinitely deep rectangular potential well and for a symmetric steep potential well of the type U(x)∞x2m. For these potential profiles and arbitrary Levy index α, we obtain the asymptotic expression of the spectral power density.

Statistics of residence time for Lévy flights in unstable parabolic potentials

2020

We analyze the residence time problem for an arbitrary Markovian process describing nonlinear systems without a steady state. We obtain exact analytical results for the statistical characteristics of the residence time. For diffusion in a fully unstable potential profile in the presence of Lévy noise we get the conditional probability density of the particle position and the average residence time. The noise-enhanced stability phenomenon is observed in the system investigated. Results from numerical simulations are in very good agreement with analytical ones.

Anomalous diffusion and nonlinear relaxation phenomena in stochastic models of interdisciplinary physics

2020

The study of nonlinear dynamical systems in the presence of both Gaussian and non-Gaussian noise sources is the topic of this research work. In particular, after shortly present new theoretical results for statistical characteristics in the framework of Markovian theory, we analyse four different physical systems in the presence of Levy noise source. (a) The residence time problem of a particle subject to a non-Gaussian noise source in arbitrary potential profile was analyzed and the exact analytical results for the statistical characteristics of the residence time for anomalous diffusion in the form of Levy flights in fully unstable potential profile was obtained. Noise enhanced stability …

Effects of solar irradiance noise on a complex marine trophic web

2022

AbstractThe analysis of experimental data of the solar irradiance, collected on the marine surface, clearly highlights the intrinsic stochasticity of such an environmental parameter. Given this result, effects of randomly fluctuating irradiance on the population dynamics of a marine ecosystem are studied on the basis of the stochastic 0-dimensional biogeochemical flux model. The noisy fluctuations of the irradiance are formally described as a multiplicative Ornstein-Uhlenbeck process, that is a self-correlated Gaussian noise. Nonmonotonic behaviours of the variance of the marine populations’ biomass are found with respect to the intensity and the autocorrelation time of the noise source, ma…

Linear and nonlinear approximations for periodically driven bistable systems

2005

We analyze periodically driven bistable systems by two different approaches. The first approach is a linearization of the stochastic Langevin equation of our system by the response on small external force. The second one is based on the Gaussian approximation of the kinetic equations for the cumulants. We obtain with the first approach the signal power amplification and output signal-to-noise ratio for a model piece-wise linear bistable potential and compare with the results of linear response approximation. By using the second approach to a bistable quartic potential, we obtain the set of nonlinear differential equations for the first and the second cumulants.

Stochastic model of memristor based on the length of conductive region

2021

Abstract We propose a stochastic model of a voltage controlled bipolar memristive system, which includes the properties of widely used dynamic SPICE models and takes into account the fluctuations inherent in memristors. The proposed model is described by rather simple equations of Brownian diffusion, does not require significant computational resources for numerical modeling, and allows obtaining the exact analytical solutions in some cases. The noise-induced transient bimodality phenomenon, arising under resistive switching, was revealed and investigated theoretically and experimentally in a memristive system, by finding a quite good qualitatively agreement between theory and experiment. B…

La storia degli orientamenti teorici: una sintesi

2015

Ampia sintesi di storia dell'antropologia socioculturale dalle origini ad oggi scritta appositamente per la seconda edizione italiana di R. Robbins, Antropologia culturale. Un approccio per problemi, UTET. Il testo del capitolo è una versione significativamente rielaborata di quella pubblicata nella prima edizione del manuale. Broad synthesis of the history of socio-cultural anthropology from its origins to the present written specifically for the second Italian edition of R. Robbins, Cultural Anthropology. A problem-solving approach, UTET. The text of the chapter is a significantly revised version of that published in the first edition of the manual.

Biological and metodological bases of muscular stretching

2008

Иностранные языки в высшей школе. Выпуск 2: Лингвистика, психология и методика обучения иностранным языкам

1975

Статьи сборника представляют собой результаты исследований по лингвистическому обоснованию, психологии и методике обучения иностранным языкам в неязыковом вузе.