Recent content by Sara Kennedy

  1. S

    I Angular momentum ladder operator derivation

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

    I Angular momentum ladder operator derivation

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

    I Angular momentum ladder operator derivation

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

    I Angular momentum ladder operator derivation

    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...
  5. S

    I Singlet and triplet spin states - the normalisation constant

    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...
  6. S

    I Singlet and triplet spin states - the normalisation constant

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

    I Singlet and triplet spin states - the normalisation constant

    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...
  8. S

    I Singlet and triplet spin states - the normalisation constant

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

    I Singlet and triplet spin states - the normalisation constant

    |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...
  10. S

    I Singlet and triplet spin states - the normalisation constant

    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.
  11. S

    I Spin up and Spin down states can be written as .... why?

    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...
  12. S

    I Spin up and Spin down states can be written as .... why?

    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...
  13. S

    I Difference between expectation value and eigenvalue

    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?
  14. S

    I Difference between expectation value and eigenvalue

    I read that a few times. Still clueless
  15. S

    I Difference between expectation value and eigenvalue

    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...
Back
Top