The noise properties of stochastic processes and entropy production

Based on a Fokker-Planck description of external Ornstein-Uhlenbeck noise and cross-correlated noise processes driving a dynamical system we examine the interplay of the properties of noise processes and the dissipative characteristic of the dynamical system in the steady state entropy production and flux. Our analysis is illustrated with appropriate examples.Comment: RevTex, 1 figure, To appear in Phys. Rev.

A semiclassical theory of quantum noise in open chaotic systems

We consider the quantum evolution of classically chaotic systems in contact with surroundings. Based on $\hbar$-scaling of an equation for time evolution of the Wigner's quasi-probability distribution function in presence of dissipation and thermal diffusion we derive a semiclassical equation for quantum fluctuations. This identifies an early regime of evolution dominated by fluctuations in the curvature of the potential due to classical chaos and dissipation. A stochastic treatment of this classical fluctuations leads us to a Fokker-Planck equation which is reminiscent of Kramers' equation for thermally activated processes. This reveals an interplay of three aspects of evolution of quantum noise in weakly dissipative open systems; the reversible Liouville flow, the irreversible chaotic diffusion which is characteristic of the system itself, and irreversible dissipation induced by the external reservoir. It has been demonstrated that in the dissipation-free case a competition between Liouville flow in the contracting direction of phase space and chaotic diffusion sets a critical width in the Wigner function for quantum fluctuations. We also show how the initial quantum noise gets amplified by classical chaos and ultimately equilibrated under the influence of dissipation. We establish that there exists a critical limit to the expansion of phase space. The limit is determined by chaotic diffusion and dissipation. Making use of appropriate quantum-classical correspondence we verify the semiclassical analysis by the fully quantum simulation in a chaotic quartic oscillator.Comment: Plain Latex, 27 pages, 6 ps figure, To appear in Physica

Interference of stochastic resonances: Splitting of Kramers' rate

We consider the escape of particles located in the middle well of a symmetric triple well potential driven sinusoidally by two forces such that the potential wells roll as in stochastic resonance and the height of the potential barrier oscillates symmetrically about a mean as in resonant activation. It has been shown that depending on their phase difference the application of these two synchronized signals may lead to a splitting of time averaged Kramers' escape rate and a preferential product distribution in a parallel chemical reaction in the steady state

Upper bound for the time derivative of entropy for nonequilibrium stochastic processes

We have shown how the intrinsic properties of a noise process can set an upper bound for the time derivative of entropy in a nonequilibrium system. The interplay of dissipation and the properties of noise processes driving the dynamical systems in presence and absence of external forcing, reveals some interesting extremal nature of the upper bound.Comment: RevTex, 13 pages, 6 figure

Proučavanje kozmološkog modela Bianchi-IX u Lyra geometriji

Some cosmological phenomena are studied from modified Einstein\u27s equations based on Lyra geometry in Bianchi-IX space-time. We study the model in the presence of a massless scalar field with a flat potential.Neke se kozmološke pojave tumače Einsteinovim jednadžbama zasnovanim na Lyra geometriji u vremenu-prostoru Bianchi-IX. Proučavamo taj model u prisutnosti bezmasenog skalarnog polja sa stalnim potencijalom

Proučavanje kozmološkog modela Bianchi-IX u Lyra geometriji

Some cosmological phenomena are studied from modified Einstein\u27s equations based on Lyra geometry in Bianchi-IX space-time. We study the model in the presence of a massless scalar field with a flat potential.Neke se kozmološke pojave tumače Einsteinovim jednadžbama zasnovanim na Lyra geometriji u vremenu-prostoru Bianchi-IX. Proučavamo taj model u prisutnosti bezmasenog skalarnog polja sa stalnim potencijalom

Awareness of vaccination status and its predictors among working people in Switzerland

BACKGROUND: Adult vaccination status may be difficult to obtain, often requiring providers to rely on individual patient recall. To determine vaccination status awareness and the sociodemographic predictors of awareness for tetanus, hepatitis A and B, tick born encephalitis (TBE) and influenza vaccination. METHODS: Multivariate analyses were used to evaluate a questionnaire survey of 10 321 employees (4070 women and 6251 men aged 15–72 years) of two companies in Switzerland. RESULTS: Among 10 321 respondents, 75.5% reported knowing their tetanus vaccination status, 64.1% hepatitis A, 61.1% hepatitis B, 64.3% TBE and 71.9% influenza. Between 1 in 4 and 1 in 3 employees were not aware of their vaccination status. Differences in awareness for the five vaccinations considered correlated with gender and language. These differences persisted in multivariate analyses. CONCLUSION: Women employees, German-speaking employees and employees who paid more attention to their diet were more often aware of their vaccination status. A more reliable and readily accessible data source for vaccination status is needed in order to capitalize on opportunities to update vaccinations among Swiss employees

Generalized quantum Fokker-Planck, diffusion and Smoluchowski equations with true probability distribution functions

Traditionally, the quantum Brownian motion is described by Fokker-Planck or diffusion equations in terms of quasi-probability distribution functions, e.g., Wigner functions. These often become singular or negative in the full quantum regime. In this paper a simple approach to non-Markovian theory of quantum Brownian motion using {\it true probability distribution functions} is presented. Based on an initial coherent state representation of the bath oscillators and an equilibrium canonical distribution of the quantum mechanical mean values of their co-ordinates and momenta we derive a generalized quantum Langevin equation in $c$-numbers and show that the latter is amenable to a theoretical analysis in terms of the classical theory of non-Markovian dynamics. The corresponding Fokker-Planck, diffusion and the Smoluchowski equations are the {\it exact} quantum analogues of their classical counterparts. The present work is {\it independent} of path integral techniques. The theory as developed here is a natural extension of its classical version and is valid for arbitrary temperature and friction (Smoluchowski equation being considered in the overdamped limit).Comment: RevTex, 16 pages, 7 figures, To appear in Physical Review E (minor revision