Talk:Ehrenfest theorem

message: Ehrenfest Principle was redirected here based on the similarity of its definition here:  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)
replies: text: 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)
thread_title: Untitled

message: 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)
thread_title:  Lindblad equation 

message: For anyone who knows any quantum mechanics, this is all obvious and hardly needs an explanation. The non-obvious part is the historical context, which should be made more prominent.
More importantly, a lay reader who's clicked on this page because it's listed as one of the fundamental concepts of quantum mechanics will be horribly lost from the first sentence.
The lead should probably start with something like "The Ehrenfest theorem, named after Paul Ehrenfest, the Austrian physicist and mathematician, describes how classical mechanics apply to the expected values of quantum wavepackets, despite not applying to the wavepackets themselves." Follow with the sentence about Heisenberg mechanics, then add some of the info from Likebox's answer to "Seems too simplistic" above, and the connection to the correspondence principle. After that, go with the rest of the existing lead. --32.154.153.34 (talk) 12:10, 21 January 2010 (UTC)
thread_title:  Far too complicated 

message: A possible source for the citation of the first formula, as well as most of the derivations, could be Griffiths. i.e. 
David J. Griffiths (2005), Introduction to Quantum Mechanics, 2nd ed., Pearson Prentice Hall
The first formula is on page 127 (eq.[3.71]). The derivation is done in chapter 3.
As I am new to editing stuff in Wikipedia: should I just go ahead and put these citations in? Is there a guideline for that?
Lompikko (talk) 09:38, 15 June 2012 (UTC)
replies: text: There is a reference in Henrik Smith's book "Introduction to Quantum Mechanics" displaying the exact equation used in the article.  This equation is more general and can be used to derive many other equations--LaoChen (talk)14:19, 18 June 2012 (UTC)
thread_title:  Citations 

message: This is not the place to define and promote off-mainstream thinking on "quantum motions".  You might try arguing about them
in Method_of_quantum_characteristics, but it is a crepuscular area. An introductory article for the novice is not the place to parse out the 
limitations of the concept of "quantum trajectory". It is evident that for velocity-dependent potentials all the classical correspondences you have in mind are
seriously undermined. The obvious  "Hamilton's equations" correspondence you may have in mind is already self-evident in the introduction, and the 
textbooks cited. Please desist promoting off-mainstream references in wikipedia articles.  Cuzkatzimhut (talk) 16:36, 28 February 2013 (UTC)
replies: text: Rezarahemi seems to insist that "The theorem shows that the classical and the quantum motions are equivalent when the position and momentum vectors are replaced by their corresponding expectation values."   "Equivalent" is too strong and vague a term, and distinctly unhelpful to the novice reader. No, QM and classical mechanicanics are not always equivalent, even in the expectation value sense.  In the examples underneath, the expressions for the evolution of ⟨x⟩ and ⟨p⟩ are given as a special case for elementary independent potentials, and more verbiage or references are superfluous, especially in the introduction. I cannot imagine what about the odd references insisted upon is essential for that. But, as indicated, for hamiltonians involving products of p's and x's the situation grows increasingly ambiguous. I see no point in abusing the introductory article as a surrogate of a physics newsgroup, or a public whiteboard to discuss this week's inspirations. Please take your notions elsewhere, perhaps the wiki suggested above. Cuzkatzimhut (talk) 19:36, 28 February 2013 (UTC)
thread_title: Quantum Motions inserts

message: Ehrenfest is not a mathematician.  His wife was.  This is something in the physics community that is constantly said incorrectly.  — Preceding unsigned comment added by 2610:E0:A040:CDFD:D483:ACB8:5C24:8018 (talk) 16:44, 14 November 2013 (UTC)
replies: text: I tweaked his professional label to "theoretical physicist", to at least comport with his wiki bio. The ambiguity arises from the dual status of theoretical physicists in the early  20th century. A theoretical physicist was regarded as a borderline mathematician, and you may note his 1905 Habilitationsschrift on the calculus of variations, published in a math journal, today would be classified as strictly math. Still, given his subsequent role and impact on science, today he can be safely pigeonholed as a theoretical physicist, not even a mathematical physicist. I thus acted on your implicit advice. Cuzkatzimhut (talk) 18:50, 14 November 2013 (UTC)
thread_title: Ehrenfest's professional label