Finding Ideals in RxR: A Complete Guide

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SUMMARY

The discussion focuses on identifying all ideals in the ring RxR, where R represents the real numbers. The four identified ideals are (R,0), (0,R), (R,R), and (0,0). Each of these sets satisfies the conditions of being an ideal, specifically being a subgroup under addition. Additionally, the sub-ring T={(100a,100b)|a,b are elements in R} is noted as a non-ideal due to failing the ideal property when multiplied by certain elements.

PREREQUISITES
  • Understanding of ring theory and ideals
  • Familiarity with subgroup properties in algebra
  • Knowledge of the structure of the Cartesian product of sets
  • Basic concepts of real numbers and their operations
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  • Explore subgroup criteria in algebraic structures
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  • Investigate examples of non-ideal sub-rings in RxR
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Mathematicians, algebra students, and anyone studying ring theory and ideal structures in abstract algebra will benefit from this discussion.

Rederick
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Homework Statement


Let S be a ring = RxR (real#,real#). Find all the ideals in RxR.


Homework Equations


We were told that there are only 4.

The Attempt at a Solution


I can only think of these 4 sub-rings of S, (R,0), (0,R), (R,R) and (0,0). And each seem to be ideal. Are these the correct 4? What other sub-rings of RxR are there but not ideal?
 
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Thinking more about it,T={(100a,100b)|a,b are elements in R} is a sub-ring but not ideal since (100a,100b)(1/2,1/2)=(50a,50b) which is not in T.

How would I say that in general to show that there are only 4?
 
Rederick said:
I can only think of these 4 sub-rings of S, (R,0), (0,R), (R,R) and (0,0). And each seem to be ideal. Are these the correct 4?

This looks fine to me. Just remember one condition of a set being ideal is that the set must be a subgroup of RXR under addition. You can check the properties for (R,0), (0,R), (R,R) and (0,0)

Looks

Rederick said:
What other sub-rings of RxR are there but not ideal?

ZXZ
 

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