Recent content by Sara Kennedy

Hmm okay. Not the answer I wanted but its a trend in QM!

Is there any logical formulation how it is derived? Or did someone just guess it

I would like to know where this comes from L±≡Lx±iLy

In the Griffiths textbook for Quantum Mechanics, It just gives the ladder operator to be L±≡Lx±iLy With reference to it being similar to QHO ladder operator. The book shows how that ladder operator is obtained, but it doesn't show how angular momentum operator is derived. Ive searched the...

Whats the requirement of normalisation to 1 in your first step? I saw this from another thread... normalising ψ=|1,−1> is easy as ψ∗=<1,−1| and then ψ∗ψ=<1,−1|1,−1>=2 which gives ψ= 1√2 |1,−1> for the normalised ket. I think I'm lacking understanding the requirement for normalisation in ket...

I fell asleep trying to work the problem out last night and still no wiser to where 1/√2 comes from.

Triplet s=1 |1 1> = up up |1 0> = 1/√2 ( up down + down up) |1 -1> = down down Singlet s =0 |0,0> = 1 /√2 ( up down - down up) Im being noob here... |1/2 1/2> as being up up? So |1 1> = |1/2 1/2> I see what you are telling me to do on page 187 it writes S_ (up up) = (S1_ up) up + up...

Im confused, I don't think that's the notation I've seen in this book

|1,1⟩=|1/2,1/2⟩ Im confused with what you mean with that statement. How can a state with total s=1 and m=1 equal a state with s=1/2 and m=1/2, these are orthogonal states? Parallel up spins states I believed to be |1,1> and |1.-1> On page 174 I see this. Is this along the lines of what you...

The triplet spin state with a normalisation constant of 1/√2 and the singlet spin state with the same normalisation constant... Where on Earth is this normalisation constant derived from? I've been scouring the Griffiths intro to quantum mechanics textbook and can't find info on it.

Hm okay I have the Sx matrix and a matrix in the n direction Sn. Do you know of any online notes that explain how to change from one basis to another? I found a few questions but they look like homework solutions and I was after explanations, it doesn't explain change of basis in my book. Just...

Spin up and spin down states in the x direction can be written as |Upx> = 1/ √2 ( |Upz> + |Downz> ) and |Downx> = 1/ √2 ( - |Upz> + |Downz> ) My textbook just stated the above facts without referencing why and I've been going through the spin chapter for a while now and I can't see it. Why...

Okay I see what you are saying now. ##E_1|\alpha|^2+E_2|\beta|^2## So the expectation value is not actually going to be one of the values of E... say E1 or E2, but as you said... maybe 2.5 children. Its not the mode but the mean?

I read that a few times. Still clueless

There is another topic for this but I didn't quite see it and I don't know how I've gone so far through my course not asking this simple question. So what's the difference? My thought process for hydrogen. I know it can have quantised values of energy, the energy values are the Eigen values of...