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We study higher-order small-noise fluctuation expansions for the overdamped Langevin dynamics in a quartic double-well potential. Assuming that the initial data admits a suitable expansion structure, we obtain a strong dynamical expansion…

Probability · Mathematics 2026-04-07 Lin Wang , Zhengyan Wu

We develop a new model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multi-scale flow which models turbulence. Magnetic dissipation occurs only via reconnections of flux ropes. The model…

Solar and Stellar Astrophysics · Physics 2010-06-16 Andrew W. Baggaley , Carlo F. Barenghi , Anvar Shukurov , Kandaswamy Subramanian

A quantum mechanical model is used to derive a generalized Landau-Lifshitz equation for a magnetic moment, including fluctuations and dissipation. The model reproduces the Gilbert-Brown form of the equation in the classical limit. The…

Materials Science · Physics 2009-11-07 A. Rebei , G. J. Parker

The fluctuation-dissipation theorem (FDT) is a central result in statistical physics, both for classical and quantum systems. It establishes a relationship between the linear response of a system under a time-dependent perturbation and time…

Quantum Physics · Physics 2018-05-28 Mohammad Mehboudi , Anna Sanpera , Juan M. R. Parrondo

We develop the Kazantsev theory of small-scale dynamo generation at small Prandtl numbers near the generation threshold and restore the concordance between the theory and numerical simulations: the theory predicted a power-law decay below…

Fluid Dynamics · Physics 2026-03-04 A. V. Kopyev , V. A. Sirota , A. S. Il'yn , K. P. Zybin

The role of fluctuation-dissipation relations (theorems) for the magnetization dynamics with Landau-Lifshitz-Gilbert and Bloch-Bloembergen damping terms are discussed. We demonstrate that the use of the Callen-Welton fluctuation-dissipation…

Statistical Mechanics · Physics 2009-11-11 Vladimir L. Safonov , H. Neal Bertram

Having established the fact that interacting classical kicked rotor systems exhibit long-lived prethermal phase with quasi-conserved average Hamiltonian before entering into chaotic heating regime, we use spatio-temporal fluctuation…

Statistical Mechanics · Physics 2021-09-01 Aritra Kundu , Atanu Rajak , Tanay Nag

Biodiversity and extinction are central issues in evolution. Dynamical balance among different species in ecosystems is often described by deterministic replicator equations with moderate success. However, fluctuations are inevitable,…

Populations and Evolution · Quantitative Biology 2014-11-25 Tsung-Cheng Lu , Yi-Ko Chen , Hsiu-Hau Lin , Chun-Chung-Chen

We derive deterministic equations for the evolution of non-Gaussian fluctuations in relativistic stochastic hydrodynamics. This is achieved by defining the average local Landau frame and corresponding fluctuating hydrodynamic variables.…

Nuclear Theory · Physics 2026-04-16 Xin An , Gokce Basar , Mikhail Stephanov

We consider a one-dimensional microscopic reaction-diffusion process obtained as a superposition of a Glauber and a Kawasaki dynamics. The reaction term is tuned so that a dynamical phase transition occurs in the model as a suitable…

Probability · Mathematics 2025-05-27 Benoit Dagallier , Claudio Landim

The Reynolds stress, or equivalently the average of the momentum flux, is key to understanding the statistical properties of turbulent flows. Both typical and rare fluctuations of the time averaged momentum flux are needed to fully…

Fluid Dynamics · Physics 2018-02-12 Freddy Bouchet , J. B. Marston , T. Tangarife

Using the initial-value formulation, a dynamic theory for systems evolving according to a Generalized Langevin Equation is developed, providing more restrictive conditions on the existence of equilibrium behavior and its…

Statistical Mechanics · Physics 2024-03-11 Massimiliano Giona , Giuseppe Procopio , Chiara Pezzotti

A quantum fluctuation theorem for a driven quantum subsystem interacting with its environment is derived based solely on the assumption that its reduced density matrix obeys a closed evolution equation i.e. a quantum master equation (QME).…

Statistical Mechanics · Physics 2010-03-01 Massimiliano Esposito , Shaul Mukamel

This Letter demonstrates for chaotic maps (logistic, classical and quantum standard maps (SMs)) that the exponential growth rate ($\Lambda$) of the out-of-time-ordered four-point correlator (OTOC) is equal to the classical Lyapunov exponent…

Chaotic Dynamics · Physics 2022-08-31 Miguel A P Reynoso , Guilherme J Delben , Martin Schlesinger , Marcus W Beims

We show that time-correlation functions of arbitrary order for any random variable in a statistical dynamical system can be calculated as higher-order response functions of the mean history of the variable. The response is to a ``control…

chao-dyn · Physics 2009-10-31 Gregory L. Eyink

We present the results of a numerical investigation of the turbulent kinematic dynamo problem in a high Prandtl number regime. The scales of the magnetic turbulence we consider are far smaller than the Kolmogorov dissipative scale, so that…

Astrophysics · Physics 2007-05-23 R. J. West , S. Nazarenko , J. P. Laval , S. Galtier

To describe the slow dynamics of a system out of equilibrium, but close to a dynamical arrest, we generalize the ideas of previous work to the case where time-translational invariance is broken. We introduce a model of the dynamics that is…

Disordered Systems and Neural Networks · Physics 2016-08-31 P. De Gregorio , F. Sciortino , P. Tartaglia , E. Zaccarelli , K. A. Dawson

We extend our earlier macrostatistical treatment of hydrodynamical fluctuations about nonequilibrium steady states to viscous fluids. Since the scale dependence of the Navier-Stokes equations precludes the applicability of any infinite…

Mathematical Physics · Physics 2015-06-05 Geoffrey L. Sewell

In the context of Markov evolution, we present two original approaches to obtain Generalized Fluctuation-Dissipation Theorems (GFDT), by using the language of stochastic derivatives and by using a family of exponential martingales…

Statistical Mechanics · Physics 2013-12-04 Raphael Chetrite , Shamik Gupta

In this review, we scrutinize historical and modern results on the linear response of dynamical systems to external perturbations with a particular emphasis on the celebrated relationship between fluctuations and dissipation expressed by…