Dynamical Systems – Reference on Relation Between SFTs and Wang-Tiles

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I've been looking at several papers which allude to a relation between SFTs. Namely, given an SFT $\Omega \subseteq \mathcal{A}^{\mathbb{Z}^2}$ with allowed patches $\mathcal{F}$, we can associate a set of domino\Wang tiles $T_{\mathcal{F}}$ defined by $\mathcal{F}$. The question of whether there is a periodic configuration, an $\omega\in \Omega$ such that $\vert \text{orbit}_{\mathbb{Z}^2}(\omega)\vert<\infty$, can be determined by studying the domino problem for $T_{\mathcal{F}}$.
Alternatively, given a set of Wang\domino $T$, we can choose an alphabet $ \mathcal{A}$ and get an SFT $\Omega \subseteq \mathcal{A}^{\mathbb{Z}^2}$ encoding the domino\wang problem of $T$.

Is there a good reference for this sort of relation? I've mainly found this topic discussed shortly in the prelimnaries of several papers. For example,

I was wondering if there is a good reference dealing with this relation\encoding of Wang tiles and SFTs. All these papers deal with this shortly, but I assumed that there might be a reference dealing with this relation more thoroughly, which I was not able to find.

Best Answer

I don't have a good reference at hand but I can explain the procedure. I'll use a quadruple to denote a Wang tile $T = (N,E,S,W)$ referring to the North, East, South and West edges of a tile respectively.

Easy direction: Given a set of Wang tiles $\{T_1, \ldots, T_k\}$, let $B_h$ be the set of pairs $(T_i,T_j)$ such that $T_i(E) \neq T_j(W)$ and let $B_v$ be the set of pairs $(T_i,T_j)$ such that $T_i(S) \neq T_j(N)$. Now let $\mathcal{F}_h$ be the patch of tiles with $T_j$ to the right of $T_i$, where $(T_i, T_j) \in B_h$ and let $\mathcal{F}_v$ be the patch of tiles with $T_j$ below $T_i$, where $(T_i,T_j) \in B_v$. We may now take our set of forbidden patches $\mathcal{F}$ to be given by $\mathcal{F}_h \cup \mathcal{F}_v$.

Harder direction: Let $\mathcal{A}$ be our alphabet. Given a set of forbidden patches $\mathcal{F} = \{P_i \mid 1 \leq i \leq k\}$, without loss of generality, we may assume that each of the patches is supported on an $n \times n$ square (as otherwise, just take all possible extensions of the patches to an $n \times n$ square such that $n$ is big enough to contain all the patches). Now, let $\mathcal{L}^{n,n}$ be the set of legal $n \times n$ patches. That is, $\mathcal{L}^{n,n} = \mathcal{A}^{n,n}\setminus \mathcal{F}$. Let $P_N$ be the patch one gets by deleting the northern-most row of $P$. Similarly for $P_E$, $P_S$ and $P_W$ for their respective rows/columns.

For every $P \in \mathcal{L}^{n,n}$, we define a Wang tile $T_P$ by

$$T_P(N) = (P_S, P_W, P_N, P_E).$$

So, the northern edge of $T_P$ contains all of the information of the patch $P$ except for the southern-most row, etc.

It's not too hard to see that two Wang tiles $T_P$ and $T_Q$ can only be placed next to each other if their corresponding North-South or East-West pair are identical, which is the same as saying that the patches $P$ and $Q$ overlap in a legal way.

There is now a simple local rule that takes one from a tiling with the Wang tiles $T_P$, $P \in \mathcal{L}^{n,n}$ to an element of the original SFT $X_{\mathcal{F}}$ whereby one just needs to rebuild the original patch $P$ from $T_P$ (which one can do using the labels of each of the edges) and then outputs the central element of $P$ (or round down if $n$ is even).

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