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I've been trying to understand more on "geometric" substitutions rather than just symbolic ones. As symbolic substitutions always yield FLC tilings, I wanted to know whether a tiling coming from a substitution being FLC, depends on the starting seed?

More accurately, I have a finite prototile set $\mathcal{P}$ and a substitution $S:\mathcal{P}\to \mathcal{P}^*$, where $\mathcal{P}^*$ are valid patches using the prototiles. I then take a finite seed $P_0\in \mathcal{P}^*$ and consider the sequence $P_n:=S^n(P_0)\in \mathcal{P}^*$. Then for any $k\in \mathbb{N}$, is the number of $k$-coronas occuring in $P_n$ uniformly bounded, independent of what is $P_0$?

When dealing with symbolic substitutions over a finite alphabet $\mathcal{A}$ on $\mathbb{Z}^d$, we have a bound of the form $\vert \mathcal{A} \vert^{(2k+1)^d}$ for how many $k$-coronas can appear in $P_n$, regardless of the seed.

In the geometric case, if I start with a legal seed $P_0$, then this doesn't seem like a problem. Moreover, if $\mathcal{T}$ is a tiling which is a limit of $P_n$, the uniform bound should come from the number of $k$-coronas in $\mathcal{T}$. Can it be that a legal tiling $\mathcal{T}$ has finitely many $k$-coronas, but the number of $k$-coronas in $P_n$ keeps growing? Are there conditions for the number of $k$-coronas to be uniformly bounded, regardless of the seed $P_0$?

I hope the terminology I used is coherent and would appreciate any input on this matter.

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    $\begingroup$ There exist substitutions whereby even starting from a single tile can lead to infinitely many two-tile patches. See for instance: N. P. Frank and E. A. Robinson, Jr., Generalized β-expansions, substitution tilings, and local finiteness, Trans. Amer. Math. Soc. 360 (2008). $\endgroup$
    – Dan Rust
    Commented Oct 10, 2023 at 7:11
  • $\begingroup$ @DanRust Thank you for your answer. I am looking for when can we say that the $k$-coronas can all come from a fixed finite set $\mathcal{P}_k$. I looked at the reference which led to a chapter by Robinson, "symbolic dynamics and tilings of $R^d$" . It seemed like the conditions for what I am asking are 2-patch closure and the number of $2$-coronas, coming from the original prototiles, be finite. Is this a good condition for what I'm looking for? $\endgroup$ Commented Oct 10, 2023 at 12:22
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    $\begingroup$ That sounds reasonable, yes. $\endgroup$
    – Dan Rust
    Commented Oct 10, 2023 at 12:29

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