Word of the Day

Coupling

Points to anyone who can find an attractive example of a "coupling constant" in the 18.03 sense:

http://ocw2.mit.edu/courses/mathematics/18-03-differential-equations-spring-2010/lecture-notes/MIT18_03S10_c04.pdf

anywhere else on MIT OCW's site.  (Yes, I'm asking you to do my job for me.  Got a problem with that?)