Filters

Results

**1**-**10**of**5389** Results

**1**-**10**of**5389**. Search took:**0.033**secondsSort by: date | relevance |

Mukherjee, S.; Chaudhary, G.P.

Silver Jubilee Physics Symposium: 25th year of nuclear physics and solid state physics symposium [Papers]1981

Silver Jubilee Physics Symposium: 25th year of nuclear physics and solid state physics symposium [Papers]1981

AbstractAbstract

[en] A new solution of the Fokker-Planck equation where the drift and diffusion coefficients have dependence on x but not on time is obtained. (author)

Primary Subject

Source

Department of Atomic Energy, Bombay (India); 279 p; 1981; p. 49-50; Department of Atomic Energy; Bombay (India); Nuclear physics and solid state physics symposium; Bombay (India); 28 Dec 1981 - 1 Jan 1982

Record Type

Book

Literature Type

Conference

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] We investigate variational methods for finding approximate solutions to the Fokker-Planck equation, especially in cases lacking detailed balance. These schemes fall into two classes: those in which a Hermitian operator is constructed from the (non-Hermitian) Fokker-Planck operator, and those which are based on soluble approximations to this operator. The various approaches are tested on a simple quantum-mechanical problem, a toy Fokker-Planck equation and finally on the problem of a particle moving in a potential and subject to external non-white noise. (author)

Primary Subject

Source

Available online at the Web site for the Journal of Physics. A, Mathematical and General (ISSN 4361-6447) http://www.iop.org/; Country of input: Argentina

Record Type

Journal Article

Journal

Journal of Physics. A, Mathematical and General; ISSN 0305-4470; ; v. 29(9); p. 1859-1872

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

External URLExternal URL

AbstractAbstract

[en] Langevin equations with external non-white noise are considered. A Fokker Planck equation valid in general in first order of the correlation time tau of the noise is derived. In some cases its validity can be extended to any value of tau. The effect of a finite tau in the nonequilibrium phase transitions induced by the noise is analyzed, by means of such Fokker Planck equation, in general, for the Verhulst equation under two different kind of fluctuations, and for a genetic model. It is shown that new transitions can appear and that the threshold value of the parameter can be changed. (orig.)

Primary Subject

Record Type

Journal Article

Journal

Z. Phys., B; v. 36(4); p. 357-364

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] We have established a general non-equilibrium thermodynamic formalism consistently applicable to both spatially homogeneous and, more importantly, spatially inhomogeneous systems, governed by the Langevin and Fokker-Planck stochastic dynamics with multiple state transition mechanisms, using the potential-flux landscape framework as a bridge connecting stochastic dynamics with non-equilibrium thermodynamics. A set of non-equilibrium thermodynamic equations, quantifying the relations of the non-equilibrium entropy, entropy flow, entropy production, and other thermodynamic quantities, together with their specific expressions, is constructed from a set of dynamical decomposition equations associated with the potential-flux landscape framework. The flux velocity plays a pivotal role on both the dynamic and thermodynamic levels. On the dynamic level, it represents a dynamic force breaking detailed balance, entailing the dynamical decomposition equations. On the thermodynamic level, it represents a thermodynamic force generating entropy production, manifested in the non-equilibrium thermodynamic equations. The Ornstein-Uhlenbeck process and more specific examples, the spatial stochastic neuronal model, in particular, are studied to test and illustrate the general theory. This theoretical framework is particularly suitable to study the non-equilibrium (thermo)dynamics of spatially inhomogeneous systems abundant in nature. This paper is the second of a series

Primary Subject

Source

(c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)

Record Type

Journal Article

Journal

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

External URLExternal URL

Kruse, Karsten; Iomin, Alexander, E-mail: k.kruse@physik.uni-saarland.de, E-mail: iomin@physics.technion.ac.il2008

AbstractAbstract

[en] Binding to cell surface receptors is thought to be essential for the transport of certain morphogens in developing tissues. The finite number of receptors per cell turns the tissue into a subdiffusive medium for the morphogens. We study a simple microscopic model of receptor-mediated transport and find superdiffusive spreading of morphogens. We propose that the superdiffusive spreading in a subdiffusive medium is due to a ratchet effect. A phenomenological model within the framework of the fractional Fokker-Planck equation allows us to analytically study the formation of morphogen gradients. Within this model, we show furthermore that the same features leading to the anomalous transport behavior also result in gradients that are robust against changes in the morphogen secretion rate. Together these findings show that anomalous transport in biological systems can be intimately linked to essential biological features

Primary Subject

Source

Available from http://dx.doi.org/10.1088/1367-2630/10/2/023019; Country of input: International Atomic Energy Agency (IAEA)

Record Type

Journal Article

Journal

New Journal of Physics; ISSN 1367-2630; ; v. 10(2); [10 p.]

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

No abstract available

Original Title

Vergleich von Bourret-, Kraichnan- und Fokker-Planck-Naeherung fuer das stochastische Beschleunigungsproblem

Primary Subject

Source

45. Physicists' meeting Hamburg 1981 and spring meeting Hamburg 1981 of the DPG; Hamburg, Germany, F.R; 23 - 27 Mar 1981; Published in summary form only.

Record Type

Journal Article

Literature Type

Conference

Journal

Verhandlungen der Deutschen Physikalischen Gesellschaft; ISSN 0420-0195; ; (no.4); p. 922

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] The Pawula theorem states that the generalized Fokker-Planck equation with finite derivatives greater than two leads to a contradiction to the positivity of the distribution function. Though negative values are inconsistent from a logical point of view, we show that such 'distribution functions' with negative values can be very useful from a practical point of view. For a Poisson-process, where the exact solution is known, we compare the solution of the second order Fokker-Planck equation to the solutions of Fokker-Planck equations of finite order. It turns out that for certain parameters the approximations of the distribution function and the moments are much better for some higher order and that the magnitude of negative values may be very small in the relevant region of variables. (orig.)

Primary Subject

Record Type

Journal Article

Journal

Z. Phys., B; v. 35(3); p. 313-315

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Castellanos-Jaramillo, Juan Miguel; Castellanos-Moreno, Arnulfo, E-mail: jmiguelcj@gmail.com2021

AbstractAbstract

[en] This work approaches the Michaelis-Menten model for enzymatic reactions at a nanoscale, where we focus on the quasi-stationary state of the process. The entropy and the kinetics of the stochastic fluctuations are studied to obtain new understanding about the catalytic reaction. The treatment of this problem begins with a state space describing an initial amount of substrate and enzyme-substrate complex molecules. Using the van Kampen expansion, this state space is split into a deterministic one for the mean concentrations involved, and a stochastic one for the fluctuations of these concentrations. The probability density in the fluctuation space displays a behavior that can be described as a rotation, which can be better understood using the formalism of stochastic velocities. The key idea is to consider an ensemble of physical systems that can be handled as if they were a purely conceptual gas in the fluctuation space. The entropy of the system increases when the reaction starts and slightly diminishes once it is over, suggesting: 1. The existence of a rearrangement process during the reaction. 2. According to the second law of thermodynamics, the presence of an external energy source that causes the vibrations of the structure of the enzyme to vibrate, helping the catalytic process. For the sake of completeness and for a uniform notation throughout this work and the ones referenced, the initial sections are dedicated to a short examination of the master equation and the van Kampen method for the separation of the problem into a deterministic and stochastic parts. A Fokker-Planck equation (FPE) is obtained in the latter part, which is then used as grounds to discuss the formalism of stochastic velocities and the entropy of the system. The results are discussed based on the references cited in this work. (paper)

Primary Subject

Source

Available from http://dx.doi.org/10.1088/1402-4896/abfd65; Country of input: International Atomic Energy Agency (IAEA)

Record Type

Journal Article

Journal

Physica Scripta (Online); ISSN 1402-4896; ; v. 96(8); [33 p.]

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] We show that for a particular linear Fokker-Planck operator, the explicit Chang and Cooper scheme is positive and entropy satisfying under a CFL criterion when the initial condition is positive. Then, we deduce that the distribution given by the explicit Chang and Cooper scheme converges toward a discrete Maxwellian equilibrium. (authors)

Primary Subject

Record Type

Journal Article

Journal

Communications in Mathematical Sciences; ISSN 1539-6746; ; v. 8(no.4); p. 1079-1090

Country of publication

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Yadav, H.L.; Noerenberg, W.

International conference on selected aspects of heavy ion reactions. Proceedings1982

International conference on selected aspects of heavy ion reactions. Proceedings1982

AbstractAbstract

No abstract available

Primary Subject

Source

CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France); 166 p; ISBN 2-7272--0073-0; ; May 1982; p. 59-61; International conference on selected aspects of heavy ion reactions; Saclay (France); 3 - 7 May 1982; Published in summary form only.

Record Type

Report

Literature Type

Conference

Report Number

Country of publication

Reference NumberReference Number

Related RecordRelated Record

INIS VolumeINIS Volume

INIS IssueINIS Issue

1 | 2 | 3 | Next |