Ehrenfest's Theorem

  • Thread starter majeka
  • Start date
  • #1
3
0
I have been asked to "find a solution to Ehrenfest's Theorem" (in this case for the expectation value of position, of a particle confined to a circle). What does this mean - what kind of answer should i find?
 

Answers and Replies

  • #2
248
0
Last edited by a moderator:
  • #3
3
0
Thankyou, I have searched many times on google and other search engines, and have found (as on the websites you have shown me) that

m*(d^2/dt^2)<x> = <F>

which is a result of the form that I am looking for. But instead of <x> I have <exp(I*theta)>, so a function of theta, as I am interested in a particle confined to a circle. I have not been able to find out whether or not I can still use this same equation (despite my <exp(I*theta)> not being a linear variable like <x>). Please understand my problems with this; I am not trying to get someone else to do my homework for me - if you have never found it hard to do your 'homework', then you are very lucky.
 
  • #4
10
0
I don't remember all the details, but I thought for a potential proportional to r^2, you should expect out the classical value for such quantities as force and energy. You might want to try finding the classical value of the force for a particle confined to a circle using classical lagrangian mechanics, I don't think its that hard, and compare this answer to the quantum ananlog. Just an idea.
 
  • #5
3
0
thanks!

Thanks spdf13,
I've tried what you said and I think it has worked...
Cheers!
:smile:
 

Related Threads on Ehrenfest's Theorem

  • Last Post
Replies
8
Views
4K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
1
Views
2K
Replies
3
Views
650
  • Last Post
Replies
2
Views
667
Replies
6
Views
2K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
19
Views
6K
Top