Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 1227

Dynamics of flows and maps (continuous and discrete time), including infinite-dimensional dynamics, Hamiltonian dynamics, ergodic theory.

4 votes

Global stability for dynamical systems in $R^n$

As the questioner notes in a comment, the answer is Yes for n<3. One way to create counterexamples for larger n is to use the work on the Seifert Conjecture. Start with a vector field pointing inwar …
Martin M. W.'s user avatar
  • 6,486
15 votes
Accepted

Definition of a strange attractor.

This is a good question. For some reason, terminology in dynamical systems is not standardized at all--and it's interesting to disentangle various definitions. A good book to look at is Differential e …
Martin M. W.'s user avatar
  • 6,486
13 votes

How to construct a topological conjugacy?

Your intuition is on target, since you mention the Banach fixed point theorem together with the Hartman-Grobman theorem. The proofs I've seen of Hartman-Grobman find the topological conjugacy as the f …
Martin M. W.'s user avatar
  • 6,486
9 votes

Quantitative versions of ergodic theorem

For the specific case you mention of an irrational rotation of the circle, it depends on the rotation number $r$. You can get slow asymptotic convergence for something like $$r=\sum{10^{-n!}}$$ (and y …
Martin M. W.'s user avatar
  • 6,486
3 votes
Accepted

Are $C^1$ vector fields generating an ergodic flow $C^0$ dense?

You can't always approximate by ergodic flows, because ergodic flows might not even exist. For example, on $S^2$ the Poincare-Bendixson theorem rules out ergodic flows, but there are many measure-pres …
Martin M. W.'s user avatar
  • 6,486
2 votes
Accepted

A 1 dimensional foliation of $\mathbb{R}^4$ with few compact leaves

Yes, there is. Conceptually, imagine a flow on $\mathbb{R}^3$ with a single closed orbit on the unit circle in the plane $z=0$, while every other trajectory has an increasing z-coordinate. It's then e …
Martin M. W.'s user avatar
  • 6,486
5 votes
Accepted

The Arnold cat map

Unless I'm misinterpreting the question, the SRB measure is just Lebesgue measure... the cat map is hyperbolic, preserves area, and is topologically transitive. See Theorem 3.10 and the following rema …
Martin M. W.'s user avatar
  • 6,486
3 votes

Continuity of the period for a periodic dynamical system

For $n = 2$, the answer is Yes. Topological considerations (as in the proof of the Poincare-Bendixson theorem) mean that the first-return map for a transversal to a point on a periodic orbit will be t …
Martin M. W.'s user avatar
  • 6,486
1 vote
Accepted

When does uniqueness of a stable equilibrium imply it is globally stable?

You can construct a smooth counterexample in $\mathbb{R}^2$: a function $f$ whose gradient flow has a unique equilibrium, which is also stable, but whose basin of attraction is not the entire plane. I …
Martin M. W.'s user avatar
  • 6,486
12 votes

How to understand a solenoid?

You can visualize a solenoid as part of a simple 3D dynamical system. The Wikipedia page on solenoids has excellent illustrations. If you want something even more concrete, and have some "Silly Putty" …
Martin M. W.'s user avatar
  • 6,486
9 votes
Accepted

A regularity property of transition matrices for the cat map

The reason that the matrices are alike is that, up to a multiplicative factor, each is approximately encoding $Area(T(R_i) \cap R_j))$. This is because the rational points with denominator $q$ are clo …
Martin M. W.'s user avatar
  • 6,486
3 votes
Accepted

Planar flow with bounded orbits and a single equilibrium point

(edited to include Willie Wong's idea for $C^0$ case.) This kind of flow can't exist in any dimension. Let $S$ be the unit sphere and $B$ be the open unit ball. If the origin is a global attractor for …
Martin M. W.'s user avatar
  • 6,486
3 votes

Existence of a continuous ergodic dynamical system for a given distribution?

Let $\mu$ be Lebesgue measure on $S^1$, and $\delta_P$ be a point-mass at a point $P \in S^1$. Then there is no flow on $S^1$ whose time averages lead to $\frac{1}{2}(\mu + \delta_P)$. (Consider the o …
Martin M. W.'s user avatar
  • 6,486
4 votes

Can the Reeb foliation of $S^3$ be realized as stable manifold foliation of a smooth hyperbo...

No, because it has a unique leaf that is a torus. That can't be a stable or unstable manifold; one reason is that it can't get either bigger or smaller under the action of the hyperbolic dynamical sys …
Martin M. W.'s user avatar
  • 6,486
3 votes
Accepted

A uniform upper bound for the linking number of periodic orbits of algebraic vector fields

The Lorenz equations are quadratic, and already have an infinite number of distinct knotted and linked orbits. An answer to one of your other questions has good references on Lorenz orbits, but I also …
Martin M. W.'s user avatar
  • 6,486

15 30 50 per page