Unique prime ideal factorization in domains?
$begingroup$
This is a follow-up to this question.
Let $A$ be a domain; let $mathfrak p_1,dots,mathfrak p_k$ be distinct prime ideals of $A$ such that $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $1le ile k$, $jge1$; and let $m$ and $n$ be elements of $mathbb N^k$ such that $$mathfrak p_1^{m_1}cdotsmathfrak p_k^{m_k}=mathfrak p_1^{n_1}cdotsmathfrak p_k^{n_k}$$ Can we conclude that $m$ and $n$ are equal?
user26857 proved that the answer is Yes if $A$ is noetherian (see this answer). (Of course in this case the condition $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $jge1$ is equivalent to $mathfrak p_ine(0)$.)
commutative-algebra maximal-and-prime-ideals integral-domain
$endgroup$
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$begingroup$
This is a follow-up to this question.
Let $A$ be a domain; let $mathfrak p_1,dots,mathfrak p_k$ be distinct prime ideals of $A$ such that $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $1le ile k$, $jge1$; and let $m$ and $n$ be elements of $mathbb N^k$ such that $$mathfrak p_1^{m_1}cdotsmathfrak p_k^{m_k}=mathfrak p_1^{n_1}cdotsmathfrak p_k^{n_k}$$ Can we conclude that $m$ and $n$ are equal?
user26857 proved that the answer is Yes if $A$ is noetherian (see this answer). (Of course in this case the condition $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $jge1$ is equivalent to $mathfrak p_ine(0)$.)
commutative-algebra maximal-and-prime-ideals integral-domain
$endgroup$
add a comment |
$begingroup$
This is a follow-up to this question.
Let $A$ be a domain; let $mathfrak p_1,dots,mathfrak p_k$ be distinct prime ideals of $A$ such that $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $1le ile k$, $jge1$; and let $m$ and $n$ be elements of $mathbb N^k$ such that $$mathfrak p_1^{m_1}cdotsmathfrak p_k^{m_k}=mathfrak p_1^{n_1}cdotsmathfrak p_k^{n_k}$$ Can we conclude that $m$ and $n$ are equal?
user26857 proved that the answer is Yes if $A$ is noetherian (see this answer). (Of course in this case the condition $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $jge1$ is equivalent to $mathfrak p_ine(0)$.)
commutative-algebra maximal-and-prime-ideals integral-domain
$endgroup$
This is a follow-up to this question.
Let $A$ be a domain; let $mathfrak p_1,dots,mathfrak p_k$ be distinct prime ideals of $A$ such that $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $1le ile k$, $jge1$; and let $m$ and $n$ be elements of $mathbb N^k$ such that $$mathfrak p_1^{m_1}cdotsmathfrak p_k^{m_k}=mathfrak p_1^{n_1}cdotsmathfrak p_k^{n_k}$$ Can we conclude that $m$ and $n$ are equal?
user26857 proved that the answer is Yes if $A$ is noetherian (see this answer). (Of course in this case the condition $mathfrak p_i^{j+1}nemathfrak p_i^j$ for all $jge1$ is equivalent to $mathfrak p_ine(0)$.)
commutative-algebra maximal-and-prime-ideals integral-domain
commutative-algebra maximal-and-prime-ideals integral-domain
asked Dec 31 '18 at 13:21
Pierre-Yves GaillardPierre-Yves Gaillard
13.2k23181
13.2k23181
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$begingroup$
The answer is no.
Let $G$ be the abelian group $mathbb{Z}times mathbb{Z}$ with the lexicographic order, and let $Msubset G$ be the sub-monoid of elements that are greater than or equal to $(0,0)$. Define monoid ideals $I_1:={(m,n):mgeq 1text{ or }ngeq 1}subset M$ and $I_2:={(m,n):mgeq 1}subset M$. For $jinmathbb{Z}_{geq 0}$ and $Isubset M$ an ideal, write $jI:={i_1+ldots+i_j:i_1,ldots,i_jin I}subset M$. Check that for all $j$, we have $jI_1neq (j+1)I_1$ and $jI_2neq (j+1)I_2$, but $I_1+I_2=I_2$.
We get a counterexample to your question by taking $A=k[M]$ to be the monoid ring of $M$ (where $k$ is any field), $mathfrak{p}_1=k[I_1]$, and $mathfrak{p}_2=k[I_2]$. Then $mathfrak{p}_1^jneq mathfrak{p}_1^{j+1}$ and $mathfrak{p}_2^jneq mathfrak{p}_2^{j+1}$, but $mathfrak{p}_1mathfrak{p}_2=mathfrak{p}_2$.
An alternate way to describe this example is $A=k[x,y,yx^{-1},yx^{-2},ldots]$, $mathfrak{p}_1=(x)$, $mathfrak{p}_2=(y,yx^{-1},yx^{-2},ldots)$.
$endgroup$
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$begingroup$
The answer is no.
Let $G$ be the abelian group $mathbb{Z}times mathbb{Z}$ with the lexicographic order, and let $Msubset G$ be the sub-monoid of elements that are greater than or equal to $(0,0)$. Define monoid ideals $I_1:={(m,n):mgeq 1text{ or }ngeq 1}subset M$ and $I_2:={(m,n):mgeq 1}subset M$. For $jinmathbb{Z}_{geq 0}$ and $Isubset M$ an ideal, write $jI:={i_1+ldots+i_j:i_1,ldots,i_jin I}subset M$. Check that for all $j$, we have $jI_1neq (j+1)I_1$ and $jI_2neq (j+1)I_2$, but $I_1+I_2=I_2$.
We get a counterexample to your question by taking $A=k[M]$ to be the monoid ring of $M$ (where $k$ is any field), $mathfrak{p}_1=k[I_1]$, and $mathfrak{p}_2=k[I_2]$. Then $mathfrak{p}_1^jneq mathfrak{p}_1^{j+1}$ and $mathfrak{p}_2^jneq mathfrak{p}_2^{j+1}$, but $mathfrak{p}_1mathfrak{p}_2=mathfrak{p}_2$.
An alternate way to describe this example is $A=k[x,y,yx^{-1},yx^{-2},ldots]$, $mathfrak{p}_1=(x)$, $mathfrak{p}_2=(y,yx^{-1},yx^{-2},ldots)$.
$endgroup$
add a comment |
$begingroup$
The answer is no.
Let $G$ be the abelian group $mathbb{Z}times mathbb{Z}$ with the lexicographic order, and let $Msubset G$ be the sub-monoid of elements that are greater than or equal to $(0,0)$. Define monoid ideals $I_1:={(m,n):mgeq 1text{ or }ngeq 1}subset M$ and $I_2:={(m,n):mgeq 1}subset M$. For $jinmathbb{Z}_{geq 0}$ and $Isubset M$ an ideal, write $jI:={i_1+ldots+i_j:i_1,ldots,i_jin I}subset M$. Check that for all $j$, we have $jI_1neq (j+1)I_1$ and $jI_2neq (j+1)I_2$, but $I_1+I_2=I_2$.
We get a counterexample to your question by taking $A=k[M]$ to be the monoid ring of $M$ (where $k$ is any field), $mathfrak{p}_1=k[I_1]$, and $mathfrak{p}_2=k[I_2]$. Then $mathfrak{p}_1^jneq mathfrak{p}_1^{j+1}$ and $mathfrak{p}_2^jneq mathfrak{p}_2^{j+1}$, but $mathfrak{p}_1mathfrak{p}_2=mathfrak{p}_2$.
An alternate way to describe this example is $A=k[x,y,yx^{-1},yx^{-2},ldots]$, $mathfrak{p}_1=(x)$, $mathfrak{p}_2=(y,yx^{-1},yx^{-2},ldots)$.
$endgroup$
add a comment |
$begingroup$
The answer is no.
Let $G$ be the abelian group $mathbb{Z}times mathbb{Z}$ with the lexicographic order, and let $Msubset G$ be the sub-monoid of elements that are greater than or equal to $(0,0)$. Define monoid ideals $I_1:={(m,n):mgeq 1text{ or }ngeq 1}subset M$ and $I_2:={(m,n):mgeq 1}subset M$. For $jinmathbb{Z}_{geq 0}$ and $Isubset M$ an ideal, write $jI:={i_1+ldots+i_j:i_1,ldots,i_jin I}subset M$. Check that for all $j$, we have $jI_1neq (j+1)I_1$ and $jI_2neq (j+1)I_2$, but $I_1+I_2=I_2$.
We get a counterexample to your question by taking $A=k[M]$ to be the monoid ring of $M$ (where $k$ is any field), $mathfrak{p}_1=k[I_1]$, and $mathfrak{p}_2=k[I_2]$. Then $mathfrak{p}_1^jneq mathfrak{p}_1^{j+1}$ and $mathfrak{p}_2^jneq mathfrak{p}_2^{j+1}$, but $mathfrak{p}_1mathfrak{p}_2=mathfrak{p}_2$.
An alternate way to describe this example is $A=k[x,y,yx^{-1},yx^{-2},ldots]$, $mathfrak{p}_1=(x)$, $mathfrak{p}_2=(y,yx^{-1},yx^{-2},ldots)$.
$endgroup$
The answer is no.
Let $G$ be the abelian group $mathbb{Z}times mathbb{Z}$ with the lexicographic order, and let $Msubset G$ be the sub-monoid of elements that are greater than or equal to $(0,0)$. Define monoid ideals $I_1:={(m,n):mgeq 1text{ or }ngeq 1}subset M$ and $I_2:={(m,n):mgeq 1}subset M$. For $jinmathbb{Z}_{geq 0}$ and $Isubset M$ an ideal, write $jI:={i_1+ldots+i_j:i_1,ldots,i_jin I}subset M$. Check that for all $j$, we have $jI_1neq (j+1)I_1$ and $jI_2neq (j+1)I_2$, but $I_1+I_2=I_2$.
We get a counterexample to your question by taking $A=k[M]$ to be the monoid ring of $M$ (where $k$ is any field), $mathfrak{p}_1=k[I_1]$, and $mathfrak{p}_2=k[I_2]$. Then $mathfrak{p}_1^jneq mathfrak{p}_1^{j+1}$ and $mathfrak{p}_2^jneq mathfrak{p}_2^{j+1}$, but $mathfrak{p}_1mathfrak{p}_2=mathfrak{p}_2$.
An alternate way to describe this example is $A=k[x,y,yx^{-1},yx^{-2},ldots]$, $mathfrak{p}_1=(x)$, $mathfrak{p}_2=(y,yx^{-1},yx^{-2},ldots)$.
answered Jan 3 at 0:46
Julian RosenJulian Rosen
11.8k12348
11.8k12348
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