Arfken is graduate level. Like, same level as Jackson. No one expects you to know that coming in. And Marion and Thornton is a normal amount of classical mechanics to know coming in--it'll actually be more rigorous than some people's backgrounds, and the same as everyone else's.
As far as I know, Poisson brackets work the same way as commutators, only on classical matrices rather than quantum mechanical ones.
You know more of this stuff than you think, and the rest of it (most of it, really) you probably aren't expected to know coming in. For example, most of my friends barely had any exposure to covariant/contravariant notation as undergrads, either (the only reason I did was because I took GR). It gets taught. You really aren't expected to know everything.
Really. You worry too much. Your education isn't lacking (although if you don't know complex analysis, you might want to take it ASAP--I got through without it, but I'm also an experimentalist in a branch of physics that doesn't really need it).
no subject
As far as I know, Poisson brackets work the same way as commutators, only on classical matrices rather than quantum mechanical ones.
You know more of this stuff than you think, and the rest of it (most of it, really) you probably aren't expected to know coming in. For example, most of my friends barely had any exposure to covariant/contravariant notation as undergrads, either (the only reason I did was because I took GR). It gets taught. You really aren't expected to know everything.
Really. You worry too much. Your education isn't lacking (although if you don't know complex analysis, you might want to take it ASAP--I got through without it, but I'm also an experimentalist in a branch of physics that doesn't really need it).