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Questions tagged [ideals]

An ideal is a subset of ring such that it is possible to make a quotient ring with respect to this subset. This is the most frequent use of the name ideal, but it is used in other areas of mathematics too: ideals in set theory and order theory (which are closely related), ideals in semigroups, ideals in Lie algebras.

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Let $R$ be a commutative ring with $1$ and $P$ a prime ideal. Claim in question: If $I$ is a $P$-primary ideal, then $P^n \subset I$ for some $n \in \mathbb{N}$ Context: If $R$ is noetherian, I ...
Loic's user avatar
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Let $R := \mathbb C[x_1,\dots,x_d]/J$ be an affine domain which is the coordinate ring of the affine variety $X = V(J) \subseteq \mathbb C^d$. Let $M \in R^{m\times(n+1)}$ be a matrix with entries ...
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Consider the dynamical map that terminates on all natural numbers: $f_o:x\mapsto (x+1)/2$ if $x$ odd $f_e:x\mapsto x/2$ if $x$ even This is easily proven to terminate for all natural numbers. Now ...
Robert Frost's user avatar
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For a noncommutative ring $R$ (and let's also say not necessarily with 1), there are 4 equivalent ways to say that an ideal $K$ is semiprime: If $A$ is a 2-sided ideal of R with $A^n \subset K$, then ...
Tom Parkes's user avatar
2 votes
1 answer
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How to construct an example of a ring having a number $m$ of prime ideals and a number $n$ of maximal ideals ? Please instruct me how to think this example step by step. Thanking you beforehand!!!
Pro_blem_finder's user avatar
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1 answer
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Let $R$ be a commutative ring with unity. Let $A$ and $B$ be commutative $R$-algebras. Let $\varphi: A \to B$ be an $R$-algebra homomorphism which is an epimorphism. Let $J \subseteq B$ be an ideal. ...
Elia Immanuel Auer's user avatar
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1 answer
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The following question was given in a lecture on commutative algebra as a (meant to be easy) exercise: Let $R$ be a (commutative, unital) integral domain, $K:=\operatorname{Quot}(R)$ its field of ...
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Let ${\cal I}$ and ${\cal J}$ be two ideals of the noetherian ring $R$. I am interested in when the following inclusion turns equality$\colon$ $$ (\blacklozenge) \quad {\cal I} {\cal J} \subset {\cal ...
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Set $\mathscr A = \mathbb C[x_1,\dots,x_n,y_1,\dots,y_n]$, and let $f_{i,j} = x_i y_j - x_j y_i$ denote the $2\times 2$ minors of the matrix $$ M = \begin{pmatrix} x_1 & \cdots & x_n \\ y_1 &...
zhjzwlys's user avatar
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1 answer
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Conjecture. Let $p_i$ denote the $i$th prime number, $n \in \Bbb{N}$ an arbitrary modulus, and $r \in \{0, \dots, n-1\}$ and arbitrary residue. Then $p_{nk + r} \in 6\Bbb{Z} + 1 \textbf{ i.o.}$ and $...
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1 answer
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Consider solving a linear system of the form $M\mathbf{x} = \mathbf{b}$ where the coefficient matrix has entries in $\mathbb{Z}[\sqrt{-6}]$, which is a Dedekind domain but not a principal ideal domain....
D.Matthew's user avatar
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I learned that in a commutative ring with the identity, we can set up the setting for the Zorn's lemma, and prove that every proper ideal lies in a maximal ideal. I noticed that we have to use the ...
Arfin's user avatar
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3 votes
1 answer
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I'm looking for a counterexample (or proof, but I doubt it is true) to the following claim, as I am having trouble finding one. I imagine a noncommutative ring theorist should be able to cook up a ...
Sam K's user avatar
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3 votes
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Let $S \subseteq M$ be a closed embedded submanifold of a amooth manifold M. Let $m(S)$ be the vanishing ideal of S, i.e. the set of smooth functions on M which vanish on S. Then is a smooth function $...
Ogawa's user avatar
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