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Jun 9, 2011 at 6:46 comment added vonjd @Deane: I would very much appreciate that - thank you!
May 31, 2011 at 18:30 comment added Deane Yang vonjd, any local operation can be made global (by just doing it everywhere). I'll add a few more vague comments to my answer when I get some time.
May 31, 2011 at 17:01 comment added vonjd @Deane: Now I am totally confused - on the one hand Tao says that differentiation is inherently local - and therefore easier. On the other hand I thought (and said it above) that differentiation is also global (in a way) because you are trying to find a function which satisfies the whole domain (and not only one point). Now Gowers seems to support this point. Isn't this a contradiction? The whole matter gets more and more mysterious (at least to me)...
May 31, 2011 at 16:13 comment added Deane Yang I have only circular arguments on why linearization is simpler than the reverse, namely what I say in the penultimate paragraph. Somehow linearization is formally (algebraically) a nice operator, whereas reconstructing a nonlinear function from its linearization is not. But otherwise I can understand your skepticism.
May 31, 2011 at 15:59 comment added gowers I'm not sure I buy your argument that the linearization "is somehow a simplification". True, linear functions are simple, but the linearization we perform when differentiating varies from point to point in a nonlinear way, and it's the entire derivative we're interested in here rather than just the derivative at a point. (This is particularly clear if we look at functions of more than one variable, when the derivative is a decidedly more complicated object than the original function.)
May 30, 2011 at 23:30 history answered Deane Yang CC BY-SA 3.0