Hidden Z2 symmetry


Today was a complete deja vu day. The 11 a.m. “Symmetries and Particle Physics” course repeated (nearly verbatim) the content of the 10 a.m. GR course. The professors are different, though the material is some foundational differential geometry that the former will use to describe Lie groups and that the latter will use to formulate relativity. It’s reasonable that the two courses would want to cover the same basic material to avoid assuming that students taking one course would necessarily be taking the other (though this seems like a safe assumption and it’s a bit of a pain that the 50 or so students have to walk to the next building). However, it’s a bit awkward when the equations written down on the board (or shown on slides) are exactly the same, up to the idiosyncratic choice of index names. (Who uses ‘i’ and ‘m’ as indices together? What happened to ‘i’ and ‘j’? Did they break up?)

I suspect the source of this symmetry is a common reference from which the lecturers borrowed heavily.

For what it’s worth, by the way, the symmetry was broken by different (markedly so) lecture styles. One lecturer used slides that he handed out before class… however the twist was that all the equations were whited out on the hand outs, and so students have to jot in equations as the lecture goes along. I’ve found this to be a surprisingly good approach since I get to write out the things that I really need to think about (writing helps me do this), without worrying about keeping up with writing the ‘storyline’ that is already printed out on the page.  The other lecturer seems to have notes that were just as meticulously prepared, but has chosen instead to write out every word he recites on the chalkboard (and hence he recites most of those words to the chalkboard). This does ensure that every student has a good set of notes, but it’s terribly inefficient and the lectures are forced to progress at a very slow pace.

I’ve been thinking of more productive ways to spend my time, such as discreetly doing example sheets (‘problem sets’ to Americans) or reading a textbook while in class… but this seems terribly cheeky. I realized, though, that the other students may be sympathetic, especially after a fellow Berkeley-bound physicist leaned over during the lecture and whispered, “This sucks.”

(Speaking of Berkeley-bound, my neighbor is a friend of another Berkeley-bound physicist … it’s a small world.)

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