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Given is a locally finite countable connected poset which satisfies further the following properties:

1. Let $C$ be any maximal chain ( i.e. inextendible chain) and $A$ be any antichain. Then $A$ is covered by both the sets ${\rm Past}(x)$ and ${\rm Future}(x)$ for $x$ running over $C$ i.e. $A \subset \bigcup_{x \in C} ({\rm Past}(x) \cup {\rm Future}(x))$ and where ${\rm Past}(x):=\lbrace y\mid y \leq x\rbrace$ and ${\rm Future}(x):=\lbrace y \mid x \leq y\rbrace$.

2. For any $x$, the intersection of ${\rm Past}(x)$ with any antichain is finite. Similarily for ${\rm Future}(x)$.

Questions:

   1. Is the orbit of any point $x$ by an automorphism $f$ of the poset finite?

2. Is the group of automorphisms of this poset countable?

3. As a polish group, is the group of automorphisms of the poset locally compact?


Thank you

Given is a locally finite countable connected poset which satisfies further the following properties:

1. Let $C$ be any maximal chain and $A$ be any antichain. Then $A$ is covered by both the sets $Past(x)$ {\rm Past}(x)$and$Future(x)${\rm Future}(x)$ for $x$ running over $C$ i.e. $A \subset \bigcup_{x \in C} ({\rm Past}(x) \cup {\rm Future}(x))$ and where $Past(x):=\lbrace {\rm Past}(x):=\lbrace y\mid y \leq x\rbrace$ and $Future(x):=\lbrace {\rm Future}(x):=\lbrace y \mid x \leq y\rbrace$.

2. For any $x$, the intersection of $Past(x)$ {\rm Past}(x)$with any antichain is finite. Similarily for$Future(x)$.{\rm Future}(x)$.

Questions:

   1. Is the orbit of any point $x$ by an automorphism $f$ of the poset finite?

2. Is the group of automorphisms of this poset countable?

3. As a polish group, is the group of automorphisms of the poset locally compact?


Thank you

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