•Opening
considerations:
–Disk
Stability Issues. Most of the mass
of the galaxy is in a dark halo, and stars are treated as particles
in the overall potential, so should disks even be stable?
–Note
that nearby interactions are unimportant:
Trelax/tc = (h/R)(N/(8logN)) –
“collisionless” if large. For N = 1011, the ratio of
relaxation to crossing time is about 108.