4 Dec
2010
4 Dec
'10
11:44 p.m.
Hi Ellis, to push the chemical reaction analogy further, tensoring with an identity morphism 1_Y is like having a chemical present that doesn't take part in the reaction: it's there are the beginning and end, but doesn't change. But you can't take it away (and no, it's not like a catalyst, in that your original arrow f was there to begin with), unless perhaps Y has some sort of dual or (weak) tensor inverse, and by now the analogy is stretched beyond breaking point. David [For admin and other information see: http://www.mta.ca/~cat-dist/ ]