Definition talk:Center (Abstract Algebra)/Ring

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I think the group is not $R$, but $R^*$, to avoid finding an inverse for the zero under multiplication. -- Lord Farin

No, anon edit was correct - only a group when R is a division ring. General field and it's only a semigroup. If anything, this question could be raised in the context of the "subgroup of units", perhaps.
It also raises the question about whether it makes sense to discuss the cener of any general semigroup - well, it does look as though it can be described, but whether it makes any actual sense or yield any interesting results is a different question. For some semigroups it may indeed be empty. --prime mover 02:50, 31 October 2011 (CDT)