Show that the rings Z[x] and Z are not isomorphic

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Homework Help Overview

The discussion revolves around demonstrating that the rings Z[x] and Z are not isomorphic. Participants are exploring structural properties and characteristics that differentiate these two rings.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Some participants attempt to identify specific structural properties of Z[x] that differ from Z. Others question the implications of the isomorphism ##\mathbb{Z}[x]/(x) \cong \mathbb{Z}## and its relevance to the overall problem.

Discussion Status

The discussion is ongoing, with participants raising various approaches to the problem. There is an exploration of the implications of assuming an isomorphism and the nature of ideals in Z. Some participants suggest considering the fact that Z[x] is not a principal ideal domain (PID) as a potential avenue for differentiation.

Contextual Notes

Participants note the challenge of finding specific structural differences between Z[x] and Z, as well as the constraints of the homework prompt which requires a demonstration of non-isomorphism.

Mr Davis 97
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Homework Statement


Show that the rings Z[x] and Z are not isomorphic

Homework Equations

The Attempt at a Solution


I want to show that these are not isomorphic. The thing is that I already know that ##\mathbb{Z}/(x) \cong \mathbb{Z}##, but for some reason I can't find specific structural properties of ##\mathbb{Z}[x]## that are different than ##\mathbb{Z}##
 
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##\mathbb{Z}/(x) \cong \mathbb{Z}##?
 
fresh_42 said:
##\mathbb{Z}/(x) \cong \mathbb{Z}##?
I meant to write ##\mathbb{Z}[x]/(x) \cong \mathbb{Z}##
 
What if you assumed an isomorphsm ##\varphi\, : \,\mathbb{Z}[x] \longrightarrow \mathbb{Z}##. Then ##\varphi((x)) ## is an ideal in ##\mathbb{Z}##, say ##\varphi((x)) = n\mathbb{Z}## with ##\varphi(x)=n##. What do you get if you factor this ideal on both sides?
 
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Mr Davis 97 said:

Homework Statement


Show that the rings Z[x] and Z are not isomorphic

Homework Equations

The Attempt at a Solution


I want to show that these are not isomorphic. The thing is that I already know that ##\mathbb{Z}/(x) \cong \mathbb{Z}##, but for some reason I can't find specific structural properties of ##\mathbb{Z}[x]## that are different than ##\mathbb{Z}##
Another idea is to use the fact that ##\mathbb{Z}[x]## is no PID, e.g. ##I:=\langle 2, 1+x \rangle##.
 
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