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Dynamical systems on measure spaces, invariant measures, ergodic averages, mixing properties.

3 votes
1 answer
425 views

Does the Krylov-Bogolyubov construction preserve "ergodic statistics"?

Suppose we have a compact metric space $X$, a continuous map $f \colon X \to X$, and Borel probability measures $\mu$ and $\nu$ on $X$ such that the set $$ X_{f,\mu} := \left\{ x \in X \, : \, \frac{1 …
Julian Newman's user avatar
1 vote
Accepted

Does the "random Krylov-Bogolyubov theorem" hold in a non-skew-product setting?

Okay, I've seen that the proof of an affirmative answer to both questions in the general case (with $\nu=\mu \otimes \lambda$) is not very hard: Since $X \times Y$ is compact, we can let $(k_n)$ be a …
Julian Newman's user avatar
1 vote
1 answer
75 views

Does the "random Krylov-Bogolyubov theorem" hold in a non-skew-product setting?

Informal description. Suppose I have a dynamical system $f$ defined on the product of a compact space $X$ representing the state space of an "experimentally visible" variable and a compact space $Y$ r …
Julian Newman's user avatar
2 votes
0 answers
67 views

Is it known whether 2-mixing continuous systems on a compact metric space are necessarily "p...

I asked this question on Math Stack Exchange at https://math.stackexchange.com/questions/4739742/; it received 4 upvotes, but no comments or answers even after a 450-point bounty. The question: Is i …
Julian Newman's user avatar
0 votes
Accepted

Does mixing automatically imply this seemingly stronger "uniform modulo re-ordering" version...

The answer to my question is yes!! [The assumption that $(X,\mathcal{X})$ is a standard Borel space is not needed.] A beautiful proof of a modified version of the statement has been provided by user65 …
Julian Newman's user avatar
1 vote
Accepted

Shift-ergodic stochastic processes in continuous time

Do you not also want that $\mathbb{P}_Y$ is $\phi$-invariant? In any case, yes there are extremely many continuous-time continuous-path real-valued stochastic processes whose law is ergodic under the …
Julian Newman's user avatar
9 votes
0 answers
189 views

For measure-preserving systems, is countable generatability of the invariant $\sigma$-algebr...

Let $X$ be a second countable Hausdorff topological space, let $T \colon X \to X$ be a Borel-measurable map, define the $\sigma$-algebra $\mathcal{I}=\{A \in \mathcal{B}(X) : T^{-1}(A)=A\}$, and for e …
Julian Newman's user avatar
3 votes
3 answers
588 views

Does mixing automatically imply this seemingly stronger "uniform modulo re-ordering" version...

THE QUESTION Let $(X,\mathcal{X})$ be a standard Borel space, $T \colon X \to X$ a measurable map, and $\mu$ a $T$-mixing probability measure. Is it necessarily the case that for all $A \in \mathcal …
Julian Newman's user avatar
10 votes
2 answers
551 views

Can Birkhoff's ergodic theorem for integrable functions easily be deduced from Birkhoff's er...

It seems to me that a considerably simpler proof [see below] of Birkhoff's ergodic theorem can be obtained for bounded observables than for more general $L^1$ observables. Therefore, I feel like it wo …
Julian Newman's user avatar
1 vote
0 answers
35 views

Under reasonable assumptions, is a closed invariant graph with only negative Lyapunov expone...

Let $\Omega$ and $M$ be compact $C^\infty$ manifolds, let $\theta \colon \Omega \to \Omega$ be a $C^\infty$ diffeomorphism, and let $\Theta \colon \Omega \times M \to \Omega \times M$ be a $C^\infty$ …
Julian Newman's user avatar
1 vote
0 answers
76 views

Is there a term for a linear operator on an $L^p$ space that "locally respects boundedness"?

Let $X$ be a Polish space, and $\mu$ a locally finite measure. Take any $p \in \{0\} \cup [1,\infty)$. We will say that a linear operator $T \colon L^p(\mu) \to L^p(\mu)$ has property $(\ast)$ if ever …
Julian Newman's user avatar
1 vote
0 answers
72 views

Is there a name for and/or reasonably nice characterisation of "mixingly physical" measures?

Let $M$ be a Riemannian manifold with volume measure $\lambda$, let $f \colon M \to M$ be a diffeomorphism, and let $\mu$ be a probability measure on $M$ with compact support. As stated in the questio …
Julian Newman's user avatar
3 votes
0 answers
102 views

Is there a term for a not-necessarily-convex set whose non-extreme points can be expressed a...

This question was asked on Math.SE here, but received no replies after several months. So I have posted it here, though with somewhat revised structuring of the question. Let $V$ be a real vector s …
Julian Newman's user avatar
1 vote
0 answers
103 views

Is there a research direction within dynamical systems theory / ergodic theory that concerns...

Let $X$ be a set equipped with some structure (e.g. topological space, measurable space, probability space, etc.). We say that two endomorphisms $f,g \colon X \to X$ are conjugate to each other if the …
Julian Newman's user avatar
0 votes
1 answer
82 views

In smooth stochastic dynamics, if a Lebesgue-like measure is both forward-time and reverse-t...

Let $(\Omega,\mathcal{F},\mathbb{P})$ be a probability space and let $X$ be a compact connected $C^\infty$-smooth manifold. Let $F \colon \Omega \times X \to X$ and $\bar{F} \colon \Omega \times X \to …
Julian Newman's user avatar

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