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I believe that this upenn text doesn't use the 2 variable direct sum operation at all (which is not commutative), but abuses its notation to denote the direct s
by bmacho 4y ago
I believe that this upenn text doesn't use the 2 variable direct sum operation at all (which is not commutative), but abuses its notation to denote the direct sum of an indexed family. (But then he can't talk about E ∐ F which was his original goal :/)
- nextaccountic 4y ago> denote the direct sum of an indexed family. Indeed he says so, but yes he keeps using E ∐ F Why is the direct sum of an indexed family different in terms of commutativity?
- bmacho 4y agoThe direct sum of an indexed family is not a function of two variables, so it is meaningless to talk about its commutativity.