scholarly journals Conformally related Einstein-Langevin equations for metric fluctuations in stochastic gravity

2016 ◽  
Vol 94 (6) ◽  
Author(s):  
Seema Satin ◽  
H. T. Cho ◽  
Bei Lok Hu
Keyword(s):  
Langevin Equations ◽  
Stochastic Gravity ◽  
Metric Fluctuations

METRIC FLUCTUATIONS IN DE SITTER SPACETIME IN STOCHASTIC GRAVITY

2011 ◽  
Vol 20 (05) ◽  
pp. 851-860
Author(s):  
ENRIC VERDAGUER
Keyword(s):  
Stress Tensor ◽  
Scalar Fields ◽  
Matter Field ◽  
Tensor Operator ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Einstein Tensor ◽  
Sitter Spacetime ◽  
Stochastic Gravity ◽  
Metric Fluctuations

Stochastic gravity extends semiclassical gravity by allowing for a systematic and self-consistent description of the metric fluctuations produced by the quantum fluctuations of the stress tensor. The effect of minimally coupled scalar fields with arbitrary mass in de Sitter spacetime is discussed, assuming that these fields are in the Bunch–Davies de Sitter invariant vacuum. The matter field fluctuations are described by the noise kernel which is obtained from the symmetrized two-point correlation of the stress tensor operator. The noise kernel is computed in terms of de Sitter invariant bi-tensors. It turns out that in a de Sitter background the two-point function of the linearized Einstein tensor, which is gauge invariant, is directly related to the noise kernel.

Stochastic Models of Particle Trajectories in Turbulent Atmosphere Flows by Using the LANGEVIN Equations

Proceedings ◽  
2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Youssra El Qasemy ◽  
Abdelfatah Achahbar ◽  
Abdellatif Khamlichi
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Classical Method ◽  
Degradation Mechanism ◽  
Transformation Process ◽  
Langevin Equations ◽  
Turbulence Data ◽  
Power Curves ◽  
And Diffusion ◽  
Fluctuating Wind

The stochastic behavior of wind speed is a particular characteristic of wind energy production, which affects the degradation mechanism of the turbine, resulting in stochastic charging on the wind turbine. A model stochastic is used in this study to evaluate the efficiency of wind turbine power of whatever degree given fluctuating wind turbulence data. This model is based on the Langevin equations, which characterize, by two coefficients, drift and diffusion functions. These coefficients describe the behavior of the transformation process from the input wind speed to the output data that need to be determined. For this present work, the computation of drift and diffusion functions has been carried out by using the stochastic model to assess the output variables in terms of the torque and power curves as a function of time, and it is compared by the classical method. The results show that the model stochastic can define the efficiency of wind turbine generation more precisely.

scholarly journals Black hole solutions in modified gravity induced by quantum metric fluctuations

2021 ◽  
Vol 31 ◽  
pp. 100756
Author(s):  
Jin-Zhao Yang ◽  
Shahab Shahidi ◽  
Tiberiu Harko ◽  
Shi-Dong Liang
Keyword(s):  
Black Hole ◽  
Modified Gravity ◽  
Black Hole Solutions ◽  
Metric Fluctuations

scholarly journals Fokker–Planck representations of non-Markov Langevin equations: application to delayed systems

2019 ◽  
Vol 377 (2153) ◽  
pp. 20180131 ◽  
Author(s):  
Luca Giuggioli ◽  
Zohar Neu
Keyword(s):  
Langevin Equation ◽  
Complex Dynamics ◽  
Probability Distributions ◽  
Delay Systems ◽  
Langevin Equations ◽  
Delayed Systems ◽  
Temporal Features ◽  
Fokker Planck Equations ◽  
Random Fluctuations ◽  
Fokker Planck

Noise and time delays, or history-dependent processes, play an integral part in many natural and man-made systems. The resulting interplay between random fluctuations and time non-locality are essential features of the emerging complex dynamics in non-Markov systems. While stochastic differential equations in the form of Langevin equations with additive noise for such systems exist, the corresponding probabilistic formalism is yet to be developed. Here we introduce such a framework via an infinite hierarchy of coupled Fokker–Planck equations for the n -time probability distribution. When the non-Markov Langevin equation is linear, we show how the hierarchy can be truncated at n  = 2 by converting the time non-local Langevin equation to a time-local one with additive coloured noise. We compare the resulting Fokker–Planck equations to an earlier version, solve them analytically and analyse the temporal features of the probability distributions that would allow to distinguish between Markov and non-Markov features. This article is part of the theme issue ‘Nonlinear dynamics of delay systems’.

A COMMENT ON TOPOLOGICAL FIELD THEORY QUANTIZATION AND STOCHASTIC PROCESSES

1990 ◽  
Vol 05 (19) ◽  
pp. 3777-3786 ◽  
Author(s):  
L.F. CUGLIANDOLO ◽  
G. LOZANO ◽  
H. MONTANI ◽  
F.A. SCHAPOSNIK
Keyword(s):  
Field Theory ◽  
Equilibrium State ◽  
Stochastic Processes ◽  
Topological Field Theories ◽  
Topological Charge ◽  
Field Theories ◽  
Langevin Equations ◽  
Topological Field Theory ◽  
Topological Field

We discuss the relation between different quantization approaches to topological field theories by deriving a connection between Bogomol’nyi and Langevin equations for stochastic processes which evolve towards an equilibrium state governed by the topological charge.

Model reduction of multi-scale chemical Langevin equations

2011 ◽  
Vol 60 (1) ◽  
pp. 75-86 ◽  
Author(s):  
Marie-Nathalie Contou-Carrere ◽  
Vassilios Sotiropoulos ◽  
Yiannis N. Kaznessis ◽  
Prodromos Daoutidis
Keyword(s):  
Model Reduction ◽  
Langevin Equations ◽  
Multi Scale
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