Lecture Notes posted up through page 55

I have now posted the lecture notes through page 55. This finishes the notes except for the 'other topics', which have not been determined yet and won't be for a while. (Please let me know if there are any that particularly interest you.) I won't create those notes until the very end.

Reversible Systems

I was e-mailed about reversible systems because of question (1) in homework sheet 1, and here is my answer (that I am posting here because it is relevant for everybody):

I checked the definition of reversible system after the lecture to check
whether I had a typo (given the question that came up). I don't remember
what I wrote on the board, but the one in the scanned lecture notes is
correct. Because of that, I didn't bring it up again in lecture the next
time.

In fact, it should be g(x,-y) = g(x,y), so it sounds like I put an extra
minus sign in the lectures.

You want invariance under (t,y) -> (-t,-y).

Lecture Notes posted up through page 43

Read the title.

Also, homework sheet 2 has been posted for a week or so, and homework sheet 3 will be posted shortly.