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Are there some references about the following result in the literature of combinatorics?

Let $P$ be a permutation on $\{1,2,\ldots,n\}$. Let $\min P$ be the minimal number in the codomain of $P$. For example, $\min ((135)) = 1$ and $\min ((234)) = 2$. Let $\max P$ be the maximal number in the codomain of a permutation $P$. For example, $\max ((135)) = 5$ and $\max ((234)) = 4$.

We say two cycles $P_1, P_2$ do not cross each other if $\max P_1 < \min P_2$ or $\max P_2 < \min P_1$. For example, $(12)$ and $(35)$ do not cross each other; $(256)$ and $(134)$ cross each other.

I think that the following result is true.

Let $\pi, \pi_1, \pi_2$ be permutations on $\{1,2,\ldots,n\}$ such that $\pi_2 = \pi \pi_1$. Let $\pi=P_1 \cdots P_k$ be a cycle decomposition of $\pi$. Suppose that $k \geq 3$, $\pi_1, \pi_2$ are 321-avoiding, and $P_i, P_j$ cross each other for all $i \neq j, i,j\in\{1,2,\ldots,k\}$. Then $\pi_1$ is the identity permutation or $\pi_1, \pi_2$ are not comparable under the Bruhat order.

Is this result studied in the literature of combinatorics? Thank you very much.

Edit: the codomain of a permutation $P$ is the set of image of $P$. For example, when $P=(125)$, then the codomain of $P$ is $\{1,2,5\}$.

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  • $\begingroup$ @WhatsUp, I mean the set of image of $P$. For example, when $P=(125)$. Then the codomain of $(125)$ is $\{1,2,5\}$. $\endgroup$ Commented Dec 20, 2016 at 16:40
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    $\begingroup$ I think it would be good to add your definition of codomain. Is it all i with $P(i) \neq i$ ? $\endgroup$ Commented Dec 20, 2016 at 16:43
  • $\begingroup$ Let me also mention that your definition of noncrossing cycles doesn't seem to be standard. $\endgroup$ Commented Dec 20, 2016 at 16:45
  • $\begingroup$ @ChristianStump, yes, it is all $i$ with $P(i) \neq i$. I have edited the post. $\endgroup$ Commented Dec 20, 2016 at 17:00
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    $\begingroup$ The term for the set of $i$ moved by $P$ is the support of $P$. $\endgroup$ Commented Dec 20, 2016 at 17:53

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