STOCHASTIC EQUATIONS THROUGH THE EYE OF THE PHYSICIST
Basic Concepts, Exact Results and Asymptotic Approximations To order this title, and for more information, click here
By Valery Klyatskin, 1988 Research Professor of Theoretical and Mathematical Physics, Russian Academy of Science; 1977 D. Sc. in Physical and Mathematical
Sciences, Acoustical Institute, Russian Academy of Science; 1968 Ph.D. in Physical and Mathematical Sciences, Institute of Atmospheric
Physics Russian Academy of Science; 1964 M.Sc. in Theoretical Physics, Moscow Institute of Physics and Technology (FIZTEX)., Russian
Academy of Science, Russia
Description Fluctuating parameters appear in a variety of physical systems and phenomena. They typically come either as random forces/sources, or
advecting velocities, or media (material) parameters, like refraction index, conductivity, diffusivity, etc. The well known example of
Brownian particle suspended in fluid and subjected to random molecular bombardment laid the foundation for modern stochastic calculus
and statistical physics. Other important examples include turbulent transport and diffusion of particle-tracers (pollutants), or continuous
densities (''oil slicks''), wave propagation and scattering in randomly inhomogeneous media, for instance light or sound propagating
in the turbulent atmosphere.
Such models naturally render to statistical description, where the input parameters and solutions are
expressed by random processes and fields.
The fundamental problem of stochastic dynamics is to identify the essential characteristics
of system (its state and evolution), and relate those to the input parameters of the system and initial data.
This raises a host of
challenging mathematical issues. One could rarely solve such systems exactly (or approximately) in a closed analytic form, and their
solutions depend in a complicated implicit manner on the initial-boundary data, forcing and system's (media) parameters . In mathematical
terms such solution becomes a complicated "nonlinear functional" of random fields and processes.
Part I gives mathematical formulation
for the basic physical models of transport, diffusion, propagation and develops some analytic tools.
Part II and III sets up and applies
the techniques of variational calculus and stochastic analysis, like Fokker-Plank equation to those models, to produce exact or approximate
solutions, or in worst case numeric procedures. The exposition is motivated and demonstrated with numerous examples.
Part IV takes up
issues for the coherent phenomena in stochastic dynamical systems, described by ordinary and partial differential equations, like wave
propagation in randomly layered media (localization), turbulent advection of passive tracers (clustering), wave propagation in disordered
2D and 3D media.
For the sake of reader I provide several appendixes (Part V) that give many technical mathematical details needed in
the book.
Audience
Researches in physics (fluid dynamics, optics, acoustics, radiophysics), geosciences (ocean, atmosphere physics), applied mathematics
(stochastic equations), applications (coherent phenomena), Senior and postgraduate students in different areas of physics, engineering
and applied mathematics
Contents Contents
Preface
Introduction
I Dynamical description of stochastic systems
1 Examples, basic problems, peculiar features of solutions
1.1 Ordinary differential equations: initial value problems
1.1.1 Particle under the random velocity field
1.1.2 Particles under the
random velocity field
1.1.3 Particles under random forces
1.1.4 Systems with the blow-up singularities
1.1.5 Oscillator with randomly
varying frequency (stochastic parametric resonance)
1.2 Linear ordinary differential equations: boundary-value problems
1.2.1 Plane waves
in layered media: a wave incident on a medium layer
1.2.2 Plane waves in layered media: the source inside the medium
1.2.3 Plane waves
in layered media: the two-layer model
1.3 First-order partial differential equations
1.3.1 Linear first-order partial differential equations:
passive tracer in random velocity field
1.3.2 Quasilinear equations
1.3.3 Boundary-value problems for nonlinear ordinary differential
equations
1.3.4 Nonlinear first-order partial differential equations
1.4 Partial differential equations of higher orders
1.4.1 Stationary
problems for Maxwell's equations
1.4.2 The Helmholtz equation (boundary-value problem) and the parabolic equation of quasioptics (waves
in randomly inhomogeneous media)
1.4.3 The Navier?Stokes equation: random forces in hydrodynamic theory of turbulence
1.4.4 Equations
of geophysical hydrodynamics
1.5 Solution dependence on medium parameters and initial value
1.5.1 Principle of dynamic causality
1.5.2
Solution dependence on initial value
2 Indicator function and Liouville equation
2.1 Ordinary differential equations
2.2 First-order
partial differential equations
2.2.1 Linear equations
2.2.2 Quasilinear equations
2.2.3 General-form nonlinear equations
2.3 Higher-order
partial differential equations
2.3.1 Parabolic equation of quasioptics
2.3.2 Random forces in hydrodynamic theory of turbulence
II Stochastic
equations
3 Random quantities, processes and fields
3.1 Random quantities and their characteristics
3.2 Random processes, fields, and
their characteristics
3.2.1 General remarks
3.2.2 Statistical topography of random processes and fields
3.2.3 Gaussian random process
3.2.4 Discontinuous random processes
3.3 Markovian processes
3.3.1 General properties
3.3.2 Characteristic functional of the Markovian
process
4 Correlation splitting
4.1 General remarks
4.2 Gaussian process
4.3 Poisson process
4.4 Telegrapher's random process
4.5 Generalized
telegrapher's random process
4.6 General-form Markovian processes
4.7 Delta-correlated random processes
4.7.1 Asymptotic meaning of delta-correlated
processes and fields
5 General approaches to analyzing stochastic dynamic systems
5.1 Ordinary differential equations
5.2 Partial differential
equations
5.2.1 Passive tracer transfer in random field of velocities
5.2.2 Parabolic equation of quasi-optics
5.2.3 Random forces in
the theory of hydrodynamic turbulence
5.3 Stochastic integral equations (methods of quantum field theory in the dynamics of stochastic
systems)
5.3.1 Linear integral equations
5.3.2 Nonlinear integral equations
5.4 Completely solvable stochastic dynamic systems
5.4.1
Ordinary differential equations
5.4.2 Partial differential equations
5.5 Delta-correlated fields and processes
5.5.1 One-dimensional
nonlinear differential equation
5.5.2 Linear operator equation
5.5.3 Partial differential equations
6 Stochastic equations with the
Markovian fluctuations of parameters
6.1 Telegrapher's processes
6.1.1 System of linear operator equations
6.1.2 One-dimension nonlinear
differential equation
6.1.3 Particle in the one-dimension potential field
6.1.4 Ordinary differential equation of the n-th order
6.1.5
Statistical interpretation of telegrapher's equation
6.2 Generalized telegrapher's process
6.2.1 Stochastic linear equation
6.2.2 One-dimensional
nonlinear differential equation
6.2.3 Ordinal differential equation of the n-th order
6.3 Gaussian Markovian processes
6.3.1 Stochastic
linear equation
6.3.2 Ordinal differential equation of the n-th order
6.3.3 The square of the Gaussian Markovian process
6.4 Markovian
processes with finite-dimensional phase space
6.4.1 Two-state process
6.5 Causal stochastic integral equations
6.5.1 Telegrapher's random
process
6.5.2 Generalized telegrapher's random process
6.5.3 Gaussian Markovian process
III Asymptotic and approximate methods for analyzing
stochastic equations
7 Gaussian random field delta-correlated in time (ordinary differential equations)
7.1 The Fokker?Planck equation
7.2 Transitional probability distributions
7.3 Applicability range of the Fokker?Planck equation
7.3.1 Langevin equation
8 Methods for
solving and analyzing the Fokker-Planck equation
8.1 System of linear equations
8.1.1 Wiener random process
8.1.2 Logarithmic-normal
random process
8.2 Integral transformations
8.3 Steady-state solutions of the Fokker?Planck equation
8.3.1 One-dimensional nonlinear
differential equation
8.3.2 Hamiltonian systems
8.3.3 Systems of hydrodynamic type
8.4 Boundary-value problems for the Fokker-Planck
equation (transfer phenomena)
8.4.1 Transfer phenomena in regular systems
8.4.2 Transfer phenomena in singular systems
8.5 Asymptotic
and approximate methods of solving the Fokker-Plank equation
8.5.1 Asymptotic expansion
8.5.2 Method of cumulant expansions
8.5.3 Method
of fast oscillation averaging
9 Gaussian delta-correlated random field (causal integral equations)
9.1 Causal integral equation
9.2 Statistical
averaging
10 Diffusion approximation
IV Coherent phenomena in stochastic dynamic systems
11 Passive tracer clustering and diffusion
in random hydrodynamic flows
11.1 General remarks
11.2 Statistical description
11.2.1 Lagrangian description (particle diffusion)
11.2.2
Eulerian description
11.3 Additional factors
11.3.1 Plane-parallel mean shear
11.3.2 Effect of molecular diffusion
11.3.3 Consideration
of finite temporal correlation radius
12 Wave localization in randomly layered media
12.1 Statistics of scattered field at layer boundaries
12.1.1 Reflection and transmission coefficients
12.1.2 Source inside the layer of a medium
12.1.3 Statistical energy localization
12.1.4 Diffusion approximation
12.2 Statistical description of a wave field in random medium
12.2.1 Normal wave incidence on the layer
of random media
12.2.2 Plane wave source located in random medium
12.2.3 Numerical simulation
12.3 Eigenvalue and eigenfunction statistics
12.3.1 General remarks
12.3.2 Statistical averaging
12.4 Multidimensional wave problems in layered random media
12.4.1 Nonstationary
problems
12.4.2 Point source in randomly layered medium
12.5 Two-layer model of the medium
12.5.1 Formulation of boundary-value problems
12.5.2 Statistical description
13 Wave propagation in random inhomogeneous medium
13.1 Method of stochastic equation
13.1.1 Stochastic
equations and their implication
13.1.2 Delta-correlated approximation of the media parameters
13.1.3 Conditions for the applicability
of the delta-correlation approximation of the medium parameters fluctuations, and diffusion approximation for the wave field
13.1.4 Wavefield
amplitude?phase fluctuations (the Smooth Perturbation Method)
13.2 Geometrical optics approximation in randomly inhomogeneous media
13.2.1 Ray diffusion in random media (Lagrangian description)
13.2.2 Caustics formation in randomly inhomogeneous media
13.2.3 Wavefield
amplitude?phase fluctuations (Eulerian description)
13.3 Method of path integral
13.3.1 Statistical description of wavefield
13.3.2
Asymptotical analysis of intensity fluctuations of plane wave
13.3.3 Caustical structure of wavefield in random media
14 Some problems
of statistical hydrodynamics
14.1 Quasicompressible properties of isotropic and stationar noncompressible turbulent media
14.2 Radiation
of sound by vortex systems
14.2.1 Sound radiation by vortex lines
14.2.2 Sound radiation by vortex rings
V Appendix
A Variation (functional)
derivatives
B Fundamental solutions of wave problems in empty and layered media
B.1 The case of empty space
B.2 The case of layered
space
C Imbedding method in boundary-value wave problems
C.1 Boundary-value problems for ordinary differential equations
C.2 Stationary
boundary-value wave problems
C.2.1 One-dimensional stationary boundary-value wave problems
C.2.2 Waves in periodically inhomogeneous
media
C.2.3 Boundary-value stationary nonlinear wave problem of self-action
C.2.4 Stationary multidimensional boundary-value problem
C.3 One-dimensional nonstationary boundary-value wave problem
C.3.1 Nonsteady medium
C.3.2 Steady medium
C.3.3 One-dimensional nonlinear
wave problem
Bibliography
Index
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