6 Oct
2016
6 Oct
'16
6:42 a.m.
Objects {A, B}, Arrows: f: A --> B, g: B --> A, denote s = gf, t = fg. equations: ss = s tt = t, it follows fs = tf, gt = sg. the hom sets are all of cardinality 2. did fast checking, needs careful checking to be sure. e. El 10/4/16 a las 15:21, Michael Barr escribi??:
We all know that if Hom(A,-) is naturally equivalent to Hom(B,-), then A is isomorphic to B. But can you find a category in which for each object C, Hom(A,C) is isomorphic to Hom(B,C) but no naturality of the isomorphism without A being isomorphic to B?
Michael
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