...Prove Their Worth...

"Problems worthy of attack
prove their worth
by hitting back." - Piet Hein

A kind of running diary and rambling pieces on my struggles with assorted books, classes, and other things, as they happen. You must be pretty bored to be reading this...

Thursday, June 06, 2002

Who is the bunny arse that thought up the Schwartzian derivative*, and more importantly, why? It looks like this, for a function f(z), with respect to z:

{f(z), z} = f'''/f'' - 3/2 * (f''/f')^2

Now, it turns out this 'derivative' has some nice properties, for instance all Mobius transformations have a vanishing Schwartzian derivative, and the reverse also works. This is cool, undeniably. But where the bloody hell does it come from?

* - Well, yes, obviously, some mother-bunny named Schwartz thought of it. Probably the same Schwartz that did work in analytic continuations. But that's not the important part.


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