11.01 Time dependent perturbation theory

[@family-accountemail9111]

Amazing what the internet can find for me! I got my chem degree 40 yrs ago i only had 3 or 4 books now i can find multiple sources excellently presented explaing what I want. My son got stuck with his qm module in his astrophysics degree and I found this for him and he is much happier!

[@jacobvandijk6525]

Couldn't agree more. It's a wonderful source of knowledge. Hope your son does well.

[@iitenergymaterialsgroup4816]

You are very welcome, I hope your son does well.

[@jacobvandijk6525]

This is a fine example of the fact that with math you can create any unphysical situation you like. Here (11:48) in first approximation the lower state is unchanged, but somehow (not physically explained, of course) the higher state in this two-state system is changed! This is truly an amazing system, haha.

[@gi99hf60]

I think you’re misunderstanding something here

[@jacobvandijk6525]

@@gi99hf60 Could be. But it seems to me you can't explain it either.

[@gi99hf60]

@@jacobvandijk6525there was a global phase common factor taken out initially, now imbedded in the w_0. This is just an artifact of that. Due to normalization, it doesn’t matter what the absolute magnitude of c_a or c_b is, but the ratio of their squares. That’s why the initial global phase factor was taken out initially, to keep one coefficient at unity and just keep all the evolution info in the other. Then we only solve one equation, it was intentionally set up that way to simplify the calculation

[@gi99hf60]

@@jacobvandijk6525 physically, the probability of being in the lower state is still decreasing just by the coefficient of the other changing. You’ll have to normalize at the end anyways

[@shadowmonarch3155]

can i get all the slides/notes taught in this video??

[@iitenergymaterialsgroup4816]

I suppose that is possible