21

It is easy to show that a PID must be noetherian. My question is:

Does UFD imply noetherian? If not, is there an easy counterexample?

I apologize if this turns out to be a simple question. Thanks in advance!

Watson
  • 23,793
minimax
  • 1,013
  • http://en.wikipedia.org/wiki/Unique_factorization_domain (see Properties and also Equivalent conditions for a ring to be a UFD* – Amzoti Dec 09 '12 at 03:39

1 Answers1

29

Since any $\,f\in k[X_1,X_2,\ldots]\;$ is a polynomial in a finite number of indeterminates $\,X_{i_1},\ldots, X_{i_n}\,$ , then in fact $\,f\in k[X_{i_1},\ldots,X_{i_n}]\;$ and this last is a UFD whenever $\,k\,$ is (in fact, this is an iff claim).

Clearly though, $\,k[X_1,\ldots]\;$ is not Noetherian since the proper ideal $\,\langle X_1,\ldots\rangle\;$ isn't finitely generated.

DonAntonio
  • 211,718
  • 17
  • 136
  • 287