A relation between max-spectrum and spectrum of a ring

622 Views Asked by At

For a commutative ring $R $ with identity we know that if the prime spectrum, the set of all prime ideal with Zariski topology, is noetherian then max spectrum, the set of all maximal ideal, is also noetherian as a subspace. I am looking for a equivalent condition for $R $ under which the conversation be true.

Note that a topological space  is called noetherian if it satisfies the descending chain condition for closed subsets

1

There are 1 best solutions below

3
On

If we denote $Spm(R)$ the maximal spectrum of $R$, then $Spm(R)$ is a Noetherian topological space (with the topology induces from $Spec(R)$ with the Zariski topology) at least if:

  1. $R$ is a Noetherian ring;
  2. $R$ is a semilocal ring, that is a ring with finite maximal ideals; in particular the local rings, that is the ring with a one maximal ideal.

As we know, if $\mathbb{K}$ is a field and $x$ is an indeterminate on $\mathbb{K}$, then $\mathbb{K}[x]$ is a Noetherian non (semi)local ring.

But there exist semilocal non Noetherian rings, for example: if $\mathbb{K}$ is a field and $\{x_1,\dots,x_n,\dots\}_{n\in\mathbb{N}}$ is a infinite many countable family of indeterminates on $\mathbb{K}$, then $R=\mathbb{K}[x_n\mid n\in\mathbb{N}]_{\displaystyle/(x_n\mid n\in\mathbb{N})^2}=\mathbb{K}[\epsilon_n\mid n\in\mathbb{N}]$ is a local ring with maximal ideal $(\epsilon_n\mid n\in\mathbb{N})$; trivially $R$ is a local non Noetherian ring and moreover $Spec(R)=Spm(R)=\{(\epsilon_n\mid n\in\mathbb{N})\}$ is (obviously) a Noetherian topological space.

Without change the names, you can consider the ring $\prod_1^mR=S$, $S$ is a semilocal non Noetherian ring and again: $Spec(S)=Spm(S)$ is a Noetherian topological space with $m$ elements.

From all this, one can draw up a list of families of rings $R$ such that $Spm(R)$ are Noetherian topological spaces.