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Let $R$ be a UFD having height one primary ideals $\mathfrak q_1,...,\mathfrak q_r$. My purpose is to show that their intersection is principal.

I do know that in a UFD each prime ideal of height one is principal.

Thanks for any help!

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A height one primary ideal in a UFD is principal and generated by a power of a prime.

Let $\mathfrak q$ be a $\mathfrak p$-primary ideal of height one. Then $\mathfrak p=(p)$ with $p\in R$ a prime element. We have $\mathfrak q\subseteq (p)$. Suppose $\mathfrak q\subseteq (p^n)$, and $\mathfrak q\nsubseteq(p^{n+1})$. Since $\sqrt{\mathfrak q}=(p)$, there is $k\ge 1$ such that $p^k\in\mathfrak q$. Then $k=n$, so $(p^n)\subseteq\mathfrak q$.

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    $\begingroup$ What happens if $q \subset \cap_{n \geq 0}(p^{n}) ?$ I mean why it cannot happen ? $\endgroup$ – user371231 Nov 7 '18 at 7:48
  • $\begingroup$ @user371231 In a UFD which elements are divisible by $p^n$, for every $n\ge 1$? $\endgroup$ – user26857 Nov 7 '18 at 17:57
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    $\begingroup$ Ok, thank you. It is elementary but seems to me very useful. $\endgroup$ – user371231 Nov 7 '18 at 19:45

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