Talk:Ehrenfest theorem
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Ehrenfest Principle was redirected here based on the similarity of its definition here: [1] to the main article Ehrenfest theorem. Also there was no reference to Ehrenfest Principle that I could find at www.britannica.com. Diverman 03:37, 22 March 2006 (UTC) (B.App.Sc.)
I will have to write an article on Ehrenfest's Principle - it is indeed a different subject than the one in this article and should not redirect here.--J S Lundeen 11:54, 13 April 2006 (UTC)
Shouldn't the derivatives of Phi be partial derivatives? Outside the integral they can be regular ones but inside the integral they should be partial ones, because Phi is a function of x and t.
- I think you're right. Also there's no need to assume A is time-independent, indeed it often is time dependent (e.g. H(x,p,t) if there a changing external potential V(x,t)).--Michael C. Price talk 22:33, 7 January 2007 (UTC)
[edit] This seems too simplistic
Surely putting expectatation values around Heisenbergs time evolution equations, does not a new theorem make. I'm sure the real content of Ehrenfest's theorem is not this. But I'll see what comments others make. —Preceding unsigned comment added by 65.2.102.44 (talk) 11:38, 26 March 2008 (UTC)
- Actually this is the real content--- the theorem is obvious in Heisenberg mechanics. It is called a theorem because it was first proven in Schrodinger's picture, where it was not anywhere near as obvious, and was actually suprising because wavepackets spread out. What Ehrenfest showed was that even though wavefunctions spread, the expected values obey Newton's laws. Note that the expected value of the position could be halfway between two big lumps of wavefunction which are nozero very far away from the central point. Nevertheless, the expected value of the position and the expected value of the momentum obey Newton's law. Again, the theorem follows from the equivalence of Heisenberg and Schrodinger's formulation, but in Heisenberg's formulation it is built in.Likebox (talk) 06:31, 9 May 2008 (UTC)
[edit] Lindblad equation
This is really a red herring--- it describes dissipative systems. I don't even think that the Eherenfest theorem is strictly true when the Lindblad operators are nonzero.Likebox (talk) 06:31, 9 May 2008 (UTC)
