I’m giving an exam this morning, and there’s yet another job talk at lunch, followed by an afternoon of trying to finish all the stuff that’s been pushed aside by candidate talks and interviews, so I’m a little too busy for detailed blogging. Sounds like time for a couple of audience participation entries…
I’m running out of good Dorky Poll topics, having already done fundamental forces, fundamental particles, and the like. This one may be too arcane, but what the hell:
What’s your favorite example of an elision in a textbook or paper?
That is, what’s the best trick you’ve seen for skipping over some unpleasant calculation or discussion? The canonical form is something like “The interested reader can show that…,” where the “showing” takes several lines of tricky algebra, but there are lots of variants. Another classic technique is to make the unpleasant derivation into an end-of-chapter problem. I have an entire math methods textbook that is practically useless as a reference because any property you might want to look up (the asymptotic behavior of Bessel functions, say) is not just left as an exercise for the reader, but assigned as an exercise for the reader.
My personal favorite comes from an undergraduate quantum mechanics book, which skips over a point in the derivation of the Bloch functions for a particle in a periodic potential with “A few minutes’ thought will show that…” Even the professor teaching the class stopped to note this one, pointing out that it required not just a few minutes’ though, but three full pages of algebra….
So what’s your favorite lazy-author trick?