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

4 votes

Dynamic of $SL_2(\mathbb{Z}$) on $\mathbb{C}^2$

The dynamics are ergodic with respect to Lebesgue measure. See G. Hedlund, Fuchsian groups and mixtures, Ann. of Math. Volume 40, Number 2 (1939) 370-383, available here. If you prefer somethi …
Vidit Nanda's user avatar
  • 15.5k
4 votes
Accepted

Knots and Dynamics. Recent breakthroughs?

It's not clear when Ghys made the slides to which you have linked. The only date I could find in those was 1963 (referring to the Lorenz equations), which would make the bound on "recent" rather gener …
Vidit Nanda's user avatar
  • 15.5k
0 votes
Accepted

A notion of a 'coarse', parametrized dimension of an object, where the parameter determines ...

A few observations first: I assume in your motivating example that the coarseness parameter $\epsilon$ is smaller than $1$, otherwise you can't even tell that cylinder apart from a point. Anton's co …
Vidit Nanda's user avatar
  • 15.5k
21 votes
2 answers
1k views

How does it End?

A recent project has forced my colleague and me to take a rather abstract approach to dynamical systems, and the following definition arose naturally in that context. Let $\mathcal{C}$ be a category. …
Vidit Nanda's user avatar
  • 15.5k
8 votes
1 answer
766 views

What information can one recover from the induced map on homology?

The following question came up while constructing delay embeddings of time series data. Consider an unknown topological space $X$ and an unknown continuous function $f:X \to X$. We are given a combin …
Vidit Nanda's user avatar
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34 votes
4 answers
5k views

Is there a categorical treatment of dynamical systems?

Let $X$ be a set and $(T,\cdot)$ an abelian group. Is there a category of $T$-dynamical systems on $X$ which yields useful information about $X$ and $T$? More precisely, is there a category whose obj …
Vidit Nanda's user avatar
  • 15.5k
5 votes

Finite-space dynamical systems

Not all interesting examples come from algebraic geometry and number theory -- your questions are fairly natural in many other settings. For instance, Conway's game of life qualifies as an answer to y …
Vidit Nanda's user avatar
  • 15.5k
1 vote
Accepted

Sets invariant under sections

Your setup defines set-valued dynamics on $X$. More precisely, you have $$X \stackrel{p}{\leftarrow} \overline{G} \stackrel{q}{\rightarrow} X$$ where $p$ and $q$ are the obvious projection maps. The s …
Vidit Nanda's user avatar
  • 15.5k
22 votes
Accepted

fixed point property for maps of compacts

Lovely question! Sadly, the answer is "no" in the sense that the fixed point property is not homotopy-invariant even in the category of finite polyhedra. In fact, it is also not invariant under the op …
Vidit Nanda's user avatar
  • 15.5k
7 votes

Good books on Geometric Theory of Dynamical Systems

Pick up (almost) anything by Ethan Akin. I particularly recommend "The General Topology of Dynamical Systems" available on Amazon. Although it is somewhat older than what you indicate you are looking …
11 votes
0 answers
202 views

Fundamental groups of reduced subgroup lattices

Let $G$ be a group. Its subgroup lattice, denoted $\Sigma G$, consists of all subgroups of $G$ partially ordered by inclusion. The topology of this poset is quite trivial, since it always has a maxima …
Vidit Nanda's user avatar
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47 votes
6 answers
5k views

Can we actually find any fixed points with Brouwer's theorem?

Background At the risk of greatly oversimplifying matters, let me state a heuristic from Granas and Dugundji's beautiful book: fixed point theorems fall into two broad categories. The first class is …
Vidit Nanda's user avatar
  • 15.5k
5 votes
Accepted

Persistent homology of Markovian dynamical systems

The answer to the question as stated seems to be "no". Consider a three-element Markov partition $\mathcal{M} = \{A, B, C\}$ with directed edges $(A,B)$, $(B,C)$ and $(C,A)$. There is an obvious peri …
Vidit Nanda's user avatar
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14 votes
2 answers
1k views

Symmetric group action on squarefree polynomials

The following dynamical system on polynomials comes mostly from idle curiosity, but I hope it is of some interest. Background Fix some natural number $n$. Let $P$ be the quotient of the polynomial ri …
Vidit Nanda's user avatar
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