# Search results

1. ### Delta function and dirac notation

Thank you for your response :)
2. ### Delta function and dirac notation

So it is wrong to normalize the function with the two delta functions that he gives using ##<a|a>=1## because it actually goes to infinity. So how could we normalize ##ψ(x)=δ(x-a)+δ(x-a)## in a correct way ?
3. ### Delta function and dirac notation

Hello there ! I found this discussion http://physics.stackexchange.com/questions/155304/how-do-we-normalize-a-delta-function-position-space-wave-function about dirac notation and delta function . The one that answers to the problem says that ##<a|a>=1## and ##<a|-a>=0## . As far as i know: 1)...
4. ### Parity and integration in spherical coordinates

Thank you very much ! :)
5. ### Parity and integration in spherical coordinates

Ok that was an easy integral but what if i have something more complicated like ##\int_{φ=0}^{2π} \int_{θ=0}^π \sin θ \ \cos θ~Y_{11}^*~Y_{1-1}~dθ \, dφ## ? If we use parity here we see that the parity of the integrated function is (-1) and the integral must be zero! No calculations ! Just used...
6. ### Parity and integration in spherical coordinates

Hello people! I have ended up to this integral ##\int_{φ=0}^{2π} \int_{θ=0}^π \sin θ \ \cos θ~Y_{00}^*~Y_{00}~dθ \, dφ## while I was solving a problem. I know that in spherical coordinates when ##\vec r → -\vec r## : 1) The magnitude of ##\vec r## does not change : ##r' → r## 2) The angles...
7. ### Orthonormality contition for radial functions of hydrogen

Thank you very much :)
8. ### Orthonormality contition for radial functions of hydrogen

Hello people ! Hope you are fine! I tried to find the inner product that u can see below, between two different radial functions. I was expecting to find zero but i found something nonzero. You can see my two questions below in the photo.
9. ### I need your opinions on Zettili's solution of an exercise

Thanks for your response to my issue !
10. ### I need your opinions on Zettili's solution of an exercise

So, in problem 3.5 he probably wanted to change the relation between ##\hat{A}## and ##|\phi_n\rangle## to ##\hat{A}## ##|\phi_n\rangle## = n ##\alpha_o\ ## ##|\phi_{n+1}\rangle## (in order not to be anymore eigenstates of ##\hat{A}## ) but forgot to mention it?
11. ### I need your opinions on Zettili's solution of an exercise

1. Homework Statement (Uploaded photo from Zettili Quantum Mechanics - Chapter 3 - Solved problems 3.4 and 3.5) Check at problem 3.4 the relation that he gives between operator A and state φn. Now check the relation that he uses in problem 3.5 between A and φn again. They are different while on...
12. ### Conservative physical quantities

Thank you very much for the help ;)
13. ### Conservative physical quantities

i am concerned about the components ! Ok, let's say that i find that [H,L]=0 (so L -angular momentum vector- is being conserved) ! Do i have to find the commutators [H,Lx] , [H,Ly] , [H,Lz] or i am sure that they will all be zero due to the fact that [H,L]=0 ?
14. ### Conservative physical quantities

Hello ppl ! If i find that a physical quantity (lets say angular momentum operator vector L) is conservative (this means [H,L]=0 - H=hamiltonian ) then its 3 components Lx , Ly and Lz are being conserved too ? That happens with every conservative vector operator ? Like spin vector S and his...
15. ### Commutators and cevi levita symbol

Thank you very much for your help :D
16. ### Commutators and cevi levita symbol

Ok i think i understand why i can't have the same index on these two . Moreover i think i found how i get rid of this minus ... I must use the fact that εijk=-εikj wright ? Is now the solution correct ? (Uploaded photo)
17. ### Commutators and cevi levita symbol

Moreover , if i use , let's say the index m on x (not on x that comes from angular momentum , yes on x that is alone) , then i still have the minus on ih bar ... My solutions say that it should not be there ...
18. ### Commutators and cevi levita symbol

I can't see why this is wrong ... :/
19. ### Commutators and cevi levita symbol

Homework Statement The problem statement can be seen in the picture i uploaded. Homework Equations - The Attempt at a Solution The attempt to the solution can be seen in the picture i uploaded. I reached to the A and i don't know how to proceed to the solution that is given below. How does...
20. ### Spherical harmonics and basis

Thank u very much for the welcome and the answer ! :)
21. ### Spherical harmonics and basis

Hello people ! I have been studying Zettili's book of quantum mechanics and found that spherical harmonics are written <θφ|L,M>. Does this mean that |θφ> is a basis? What is more, is it complete and orthonormal basis in Hilbert? More evidence that it is a basis, in the photo i uploaded , in...