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[parent] Viewing Correction to 'composite number'
Too specific, only works for positive integers. by cgibbard

Correction id: 4713
Filed on: 2004-08-29 20:51:19
Status: Accepted on 2004-09-07 12:45:50
Type: Addendum

Correction text:
It would be nice if the definition at least worked for the integers, and it's not much harder to define the notion of a composite in any UFD. The positive integers don't quite form a ring, and so definitions that work for them might need a bit more work than usual to generalise.

Defining composite as the opposite of an irreducible would likely work well.
"If R is an integral domain, then n in R is called composite if n = a b for some non-units a and b."

Or if you want to be a bit more restrictive, but better capture the idea in all useful cases (this is equivalent in the case of a UFD),
"An element n in an integral domain is called composite if it can be expressed as the product of at least two primes."

Or perhaps
"A non-unit in an integral domain is called composite if it is not irreducible."

There are other ways of course, but these seem like the most natural ones to me.

No comment from object owner mathcam.
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elementary definition by akrowne on 2004-08-30 15:21:30
I hope in addressing this correction that a more intuitive, elementary definition is preserved. Composite number is a useful concept even before one gets to the point of knowing about integral domains and so forth (or any group theory at all).

apk
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