Simple Rings: Commutativity and Identity

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Discussion Overview

The discussion revolves around the properties of simple rings, particularly focusing on the existence of a multiplicative identity and the implications for commutative simple rings being fields. Participants explore definitions and assumptions related to rings, identities, and ideals.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that all commutative simple rings are fields, but question the necessity of an identity element in this context.
  • One participant argues that if R is a simple ring and x is a nonzero element, then Rx is a nonzero ideal, leading to the conclusion that x must be invertible.
  • Another participant expresses uncertainty about the existence of an identity in R, suggesting that it needs to be established.
  • A reference to Wikipedia's definition of a ring is made, emphasizing the requirement for a multiplicative identity.
  • Some participants agree that every ring should have a multiplicative identity, questioning the assumptions of others regarding this definition.
  • There is a mention of the possibility that not all definitions of rings require an identity, indicating a divergence in understanding among participants.
  • Links to external resources are provided to support the discussion on commutative rings without identity.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity of an identity element in simple rings, with some asserting its importance while others suggest that definitions may vary. The discussion remains unresolved regarding the implications of these differing definitions.

Contextual Notes

There is a lack of clarity regarding the definitions of rings and whether an identity element is universally required. This affects the understanding of the properties of simple rings and their classification as fields.

jem05
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Hello everyone,

i was checking out a paper on simple rings
http://www.imsc.res.in/~knr/RT09/sssrings.pdf
and they said that all commutative simple rings are fields.
i just don't see why they should have identity.
thank you.
 
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Let R be a simple ring. Let x be a nonzero element of R. Then Rx is a nonzero ideal Thus Rx=R. Thus there exists y in R such that yx=1. Thus x is invertible.
 
but i don't have identity in R.
It's not given, i think we need to show it, right?
 
From Wikipedia's definition of a ring:

3. Existence of multiplicative identity. There exists an element 1 in R, such that for all elements a in R, the equation 1 · a = a · 1 = a holds.
 
yeah i agree with this,
but sorry i don't see how this is equivalent to what you did.
what is our 1 here?

after i get that R has identity,
then since {0} is a maximal ideal then R/ {0} = R is a field and I am done
 
Every ring, by definition, has a multiplicative identity that is usually denoted as 1. So where is your problem? We have proven that each simple commutative ring is a field using only the definitions and nothing more. If you still have some problem with this proof - please, be very precise. For instance I fail to understand your "{0} being a maximal ideal".
 
arkajad said:
Every ring, by definition, has a multiplicative identity that is usually denoted as 1. So where is your problem?
The problem might be that not everyone requires a ring to have an identity; it seems that jem05 is one of them. It also seems that the paper is NOT one of them (as most texts on modules and commutative algebra), so I don't see a problem any more.

\\edit: I see that jem05 still has problems with the proof after assuming R has an identity. Then I agree: please be precise about what you don't understand.
 
Landau said:
The problem might be that not everyone requires a ring to have an identity; it seems that jem05 is one of them. It also seems that the paper is NOT one of them (as most texts on modules and commutative algebra), so I don't see a problem any more.

Yeah, good point. In fact, this should have been the first thing that needed to be made clear.
 
  • #10
ok, thanks
yeah sorry for not being clearer, but yeah i assumed i have no identity for my ring R
 

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