In the AoPS Olympiad Problem Solving class today, one of the students brought to my attention the existence of a branch of mathematics called differential Galois theory. It is essentially Galois theory used on differential equations. As a result, it is possible to prove that certain functions do not possess elementary antiderivatives. I had always wondered how they did that. Now I need to find a good book on the topic. Has anyone read one?
I managed to be excessively stupid today. I dropped one of my fountain pens, and as a result, the nib got bent slightly. I have more or less repaired it now, but I’ll still probably do a bit of fiddling with it for a few days.
Most of the CDs I ordered last week arrived yesterday. I now have a recording of the Art of Fugue played by Gustav Leonhardt, a recording of the Well-Tempered Clavier book 1 played by Leonhardt, and a recording of the complete Well-Tempered Clavier played by Sviatoslav Richter. Now I’m just waiting for the Mass in B Minor.