Does the Hamilton-Jacobi equation exist for chaotic systems?

  • #1
andresB
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TL;DR Summary
Does the Hamilton-Jacobi equation exist for chaotic systems?
Given a Hamiltonian ##H(\mathbf{q},\mathbf{p})##, in the time-independent Hamilton-Jacobi approach we look for a canonical transformation ##(\mathbf{q},\mathbf{p})\rightarrow(\mathbf{Q},\mathbf{P})## such that the new Hamiltonian is one of the new momenta $$H(\mathbf{q},\mathbf{p})=K(\mathbf{Q},\mathbf{P})=P_{1}=E.$$
If such transformation exists, all the momenta ##\mathbf{P}## are constant of the motion. And, since the transformation is canonical, we will have n constant of the motion in involution, i.e., ##\left\{ P_{i},P_{j}\right\} =0.## But this seems to be the requirement of the Liouville theorem for integrability. Chaotic systems don't have that many constants of motion in involution.
This seems to imply that the Hamilton-Jacobi equations cannot be even written for chaotic systems, so my reasoning has to be wrong somewhere. Where?
 
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  • #2
andresB said:
TL;DR Summary: Does the Hamilton-Jacobi equation exist for chaotic systems?

Given a Hamiltonian H(q,p), in the time-independent Hamilton-Jacobi approach we look for a canonical transformation (q,p)→(Q,P) such that the new Hamiltonian is one of the new momenta H(q,p)=K(Q,P)=P1=E.
If such transformation exists, all the momenta P are constant o
Such a transformation exists locally outside an equilibrium. The set where this transformation is defined is not invariant. The system comes and goes away from there, while a dynamical chaos appears in invariant sets.
 
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  • #3
wrobel said:
Such a transformation exists locally outside an equilibrium. The set where this transformation is defined is not invariant. The system comes and goes away from there, while a dynamical chaos appears in invariant sets.

Ok, I suspected the issue had to do with the new momenta not being defined globally.

Yet, I'm not sure I understand your answer. Can you give more details or point to a source with an example?
 
  • #4
A dynamical chaos is an informal concept which expresses a complex of very different effects. The common feature for all these effects is a complicated behavior of trajectories of a dynamical system. Every time, one should specify what he means by saying “dynamical chaos”. For example, in Hamiltonian systems, ergodicity or separatrix splitting are commonly considered as a dynamical chaos, but there are a lot of other chaotic effects. Real life examples are really hard.
See for example this https://link.springer.com/book/10.1007/978-3-642-03028-4
or start from this https://www.mat.univie.ac.at/~gerald/ftp/book-ode/ode.pdf

UPD

Dissipative systems commonly have attractors. If an attractor is of complicated geometry, say has a fractional dimension, then trajectories which wind up on the attractor replicate its geometry and become complicated. That is another chaotic effect.
 
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  • #5
Fascinating and frustrating at the same time.

wrobel said:

My doubts started by studyng perturbation theory. In the book Canonical Perturbation Theories Degenerate Systems and Resonance, I find the following
1691594084323.png


The usual books in analytical mechanics don't deal with this.
 

Related to Does the Hamilton-Jacobi equation exist for chaotic systems?

What is the Hamilton-Jacobi equation?

The Hamilton-Jacobi equation is a formulation of classical mechanics that provides a bridge between classical and quantum mechanics. It is a partial differential equation that describes the evolution of the principal function, which can be used to determine the action and subsequently the trajectories of a system.

Can the Hamilton-Jacobi equation be applied to chaotic systems?

Yes, the Hamilton-Jacobi equation can be applied to chaotic systems. However, finding exact solutions for chaotic systems is extremely challenging due to the sensitive dependence on initial conditions and the complex nature of their trajectories.

Why is it difficult to solve the Hamilton-Jacobi equation for chaotic systems?

It is difficult to solve the Hamilton-Jacobi equation for chaotic systems because these systems exhibit highly irregular and unpredictable behavior. The solutions often require extremely precise initial conditions and can be highly sensitive to numerical errors, making analytical or even numerical solutions hard to obtain.

Are there any methods to approximate solutions to the Hamilton-Jacobi equation for chaotic systems?

Yes, there are several methods to approximate solutions to the Hamilton-Jacobi equation for chaotic systems. Techniques such as perturbation theory, numerical simulations, and the use of variational principles can provide approximate solutions. However, these methods may not always capture the full complexity of chaotic behavior.

What is the significance of solving the Hamilton-Jacobi equation for chaotic systems?

Solving the Hamilton-Jacobi equation for chaotic systems is significant because it can provide insights into the underlying mechanics of chaotic behavior and help in understanding the transition from regular to chaotic dynamics. It also has implications for various fields such as celestial mechanics, fluid dynamics, and even quantum chaos.

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