14 Nov
2002
14 Nov
'02
3:35 p.m.
O course the property is well known - see the article of S. Schanuel in Como '90 proceedings, Springer LNM 1488 (pg. 381, property 4) of section 5). Carboni. At 09.41 13/11/2002 +0000, you wrote:
Am I being dim here? In an extensive category (coproducts are preserved by pullbacks and are disjoint), can I cancel thus: X+1 ~= Y+1 ?=>? X ~= Y ?
So far I have neither a proof nor a counterexample. If this cancellation principle exists it'll be slightly subtle, since 0+N ~= 1+N, and so we'd only be able to cancel adding a restricted class of (finite?) objects.
I'd be grateful for either a proof or a counterexample!
Michael Abbott
15-Nov-2002 12:19:35 -0400,1345;000000000000-00000000