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Michael Hardy
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Let $\pi \colon X \to Y$$\pi : X \to Y$ be a factor map between subshifts over finite alphabets. Let Aut($X$)$\operatorname{Aut}(X)$ and Aut($Y$)$\operatorname{Aut}(Y)$ stand for automorphism groups of these shifts. We say that $\varphi \in$Aut(${X}$)$\varphi \in\operatorname{Aut}(X)$ is compatible with $\pi$ if $\pi(x)=\pi(x')$ for $x,x'\in X$ implies $\pi(\varphi(x))=\pi(\varphi(x'))$. If $\varphi$ is compatible with $\pi$ then one can define $\psi=\rho_{\pi}(\varphi)$$\psi=\rho_\pi(\varphi)$ on $y\in Y$ by taking $x\in X$ with $\pi(x)=y$ and setting $\psi(\pi(x)) = \pi(\varphi(x))$. Clearly, $\psi$ is an endomorphism of $Y$. Consider the following conditions

  1. $\psi=\rho_{\pi}(\varphi)$$\psi=\rho_\pi(\varphi)$ is an automorphism of $Y$ for some $\pi$-compatible automorphism $\varphi$ of $X$,

  2. every automorphism $\psi$ of $Y$ satisfies $\psi=\rho_{\pi}(\varphi)$$\psi=\rho_\pi(\varphi)$ for some automorphism $\varphi$ of $X$ compatible with $\pi$,

  3. for every $\pi$-compatible automorphism $\varphi$ of $X$ the endomorphism $\psi=\rho_{\pi}(\varphi)$$\psi=\rho_\pi(\varphi)$ is an automorphism of $Y$,

  4. every automorphism of $X$ is $\pi$-compatible.

Are there any conditions one can impose on $X$ and $Y$ to guarantee that conditionconditions (1)-(4) or conditions from some subset of {1,2,3,4}$\{1,2,3,4\}$ hold?

Let $\pi \colon X \to Y$ be a factor map between subshifts over finite alphabets. Let Aut($X$) and Aut($Y$) stand for automorphism groups of these shifts. We say that $\varphi \in$Aut(${X}$) is compatible with $\pi$ if $\pi(x)=\pi(x')$ for $x,x'\in X$ implies $\pi(\varphi(x))=\pi(\varphi(x'))$. If $\varphi$ is compatible with $\pi$ then one can define $\psi=\rho_{\pi}(\varphi)$ on $y\in Y$ by taking $x\in X$ with $\pi(x)=y$ and setting $\psi(\pi(x)) = \pi(\varphi(x))$. Clearly, $\psi$ is an endomorphism of $Y$. Consider the following conditions

  1. $\psi=\rho_{\pi}(\varphi)$ is an automorphism of $Y$ for some $\pi$-compatible automorphism $\varphi$ of $X$,

  2. every automorphism $\psi$ of $Y$ satisfies $\psi=\rho_{\pi}(\varphi)$ for some automorphism $\varphi$ of $X$ compatible with $\pi$,

  3. for every $\pi$-compatible automorphism $\varphi$ of $X$ the endomorphism $\psi=\rho_{\pi}(\varphi)$ is an automorphism of $Y$,

  4. every automorphism of $X$ is $\pi$-compatible.

Are there any conditions one can impose on $X$ and $Y$ to guarantee that condition (1)-(4) or conditions from some subset of {1,2,3,4} hold?

Let $\pi : X \to Y$ be a factor map between subshifts over finite alphabets. Let $\operatorname{Aut}(X)$ and $\operatorname{Aut}(Y)$ stand for automorphism groups of these shifts. We say that $\varphi \in\operatorname{Aut}(X)$ is compatible with $\pi$ if $\pi(x)=\pi(x')$ for $x,x'\in X$ implies $\pi(\varphi(x))=\pi(\varphi(x'))$. If $\varphi$ is compatible with $\pi$ then one can define $\psi=\rho_\pi(\varphi)$ on $y\in Y$ by taking $x\in X$ with $\pi(x)=y$ and setting $\psi(\pi(x)) = \pi(\varphi(x))$. Clearly, $\psi$ is an endomorphism of $Y$. Consider the following conditions

  1. $\psi=\rho_\pi(\varphi)$ is an automorphism of $Y$ for some $\pi$-compatible automorphism $\varphi$ of $X$,

  2. every automorphism $\psi$ of $Y$ satisfies $\psi=\rho_\pi(\varphi)$ for some automorphism $\varphi$ of $X$ compatible with $\pi$,

  3. for every $\pi$-compatible automorphism $\varphi$ of $X$ the endomorphism $\psi=\rho_\pi(\varphi)$ is an automorphism of $Y$,

  4. every automorphism of $X$ is $\pi$-compatible.

Are there any conditions one can impose on $X$ and $Y$ to guarantee that conditions (1)(4) or conditions from some subset of $\{1,2,3,4\}$ hold?

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Dominik Kwietniak
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Automorphism groups of subshifts and factor maps

Let $\pi \colon X \to Y$ be a factor map between subshifts over finite alphabets. Let Aut($X$) and Aut($Y$) stand for automorphism groups of these shifts. We say that $\varphi \in$Aut(${X}$) is compatible with $\pi$ if $\pi(x)=\pi(x')$ for $x,x'\in X$ implies $\pi(\varphi(x))=\pi(\varphi(x'))$. If $\varphi$ is compatible with $\pi$ then one can define $\psi=\rho_{\pi}(\varphi)$ on $y\in Y$ by taking $x\in X$ with $\pi(x)=y$ and setting $\psi(\pi(x)) = \pi(\varphi(x))$. Clearly, $\psi$ is an endomorphism of $Y$. Consider the following conditions

  1. $\psi=\rho_{\pi}(\varphi)$ is an automorphism of $Y$ for some $\pi$-compatible automorphism $\varphi$ of $X$,

  2. every automorphism $\psi$ of $Y$ satisfies $\psi=\rho_{\pi}(\varphi)$ for some automorphism $\varphi$ of $X$ compatible with $\pi$,

  3. for every $\pi$-compatible automorphism $\varphi$ of $X$ the endomorphism $\psi=\rho_{\pi}(\varphi)$ is an automorphism of $Y$,

  4. every automorphism of $X$ is $\pi$-compatible.

Are there any conditions one can impose on $X$ and $Y$ to guarantee that condition (1)-(4) or conditions from some subset of {1,2,3,4} hold?