Talk:Path integral formulation

"Strictly speaking the only question that can be asked in physics is: "What fraction of states satisfying condition A also satisfy condition B?""

Where does this quote come from? There's no citation. What is it even supposed to mean? Not only is this completely meaningless "generalized" semantics mumbo jumbo, it also doesn't even strike me as true. I'm not sure how something such as measuring the speed of light would be described by this question. Unless you define "states" as something dumb such as the readings on your instruments. --176.199.192.165 (talk) 18:19, 28 April 2016 (UTC)

Who is this article written for?

I view myself as a literate, relatively intelligent person. I'm interested in physics, and although I have no formal training in the field, as a hobby I have acquainted myself with a few of the basics of classical mechanics, general relativity, and quantum field theory. And still, I find this article mostly incomprehensible to me. I feel that the entire article is very technical and at no point in it is more widely accessible language used. I do not understand this particular subject well, so I can not solve this problem myself, but I'm hoping that one of the very knowledgeable people who wrote this article can! This information is so important, so fundamental to the workings of our universe. . .and yet I fear my lack of understanding will be a common experience other readers will also have. Wikipedia is an encyclopedia, and I think we need to make its information accessible to a general audience, to curious people who are not already specialists in a given field! Becca (talk) 00:26, 10 November 2017 (UTC)

To give you some concrete examples of my confusion, after trying to read this article I still don't really even know what the path integral formulation is. Is it an interpretation of quantum mechanics, comparable to the Copenhagen interpretation or the many-worlds interpretation? Or is it a specific equation like Schrodinger's equation? Or perhaps a set of equations like the Einstein field equations? Or something else entirely? After attempting to read this article, I still don't know. Also, I want to know whether the path integral formulation is supported by all particle physicists. . .or does it have some critics? What are their criticisms of it? Have experiments been conducted to try and test the formulation? Or is it the sort of thing that is not testable? As you can see, I have a lot of questions. I think the level of detail and math in this articleis excellent, but I think a more general and concise summary somewhere in the article would greatly improve it. Becca (talk) 01:09, 10 November 2017 (UTC)

Yes, the article is necessarily technical, and not a tutorial for anyone who has not mastered quantum mechanics first. It is virtually impossible to make a popularly accessible "story" about a mathematical formalism, and not merely purveying a Lie-to-children. The article states up front it is a formulation of QM, and not an interpretation. So any talk of interpretation here (beyond mathematical interpretation, a very different, technical concept) is misplaced--so, in my view, section 8 should be a footnote, and not a section, as it has potentially misled, e.g., you. It is a mathematical technique re-expressing standard QM, Schroedinger equations and all, in a language amenable to some types of calculation. But it is equivalent to the standard QM formulation, and, as such, it predicts identical experimental results as standard QM--so there could be no issue of "testing" it or "criticizing" it. I can't help feeling you are in the wrong article here. Popular science publications are aggressively awful at summarizing such things, and create torrents of misconceptions impossible to resolve in WP, so a simple physics book could serve as a sensible tutorial. Cuzkatzimhut (talk) 15:10, 10 November 2017 (UTC)

Thank you very much for your response, Cuzkatzimhut! And thanks to you, I have a much better idea of what the path integral formulation is. I was specifically helped by this section of your comment: "it is a mathematical technique re-expressing standard QM, Schroedinger equations and all, in a language amenable to some types of calculation. But it is 'equivalent' to the standard QM formulation, and, as such, it predicts identical experimental results as standard QM--so there 'could' be no issue of 'testing' it or 'criticizing' it." That's great! And honestly, I think some language like that would be an excellent addition to the opening of this article. With due respect, however, I do disagree with you on what function this article should serve. You say that this article is only written for people who have already mastered quantum mechanics. However, according to Wikipedia's policy WP:NOT, Wikipedia should be an encyclopedia for a general audience--NOT a scientific journal or research paper. The policy reads: "A Wikipedia article should not be presented on the assumption that the reader is well-versed in the topic's field. Introductory language in the lead (and also maybe the initial sections) of the article should be written in plain terms and concepts that can be understood by any literate reader of Wikipedia without any knowledge in the given field before advancing to more detailed explanations of the topic." This Wikipedia policy (like all Wikipedia policies) is binding, and it's what I'm advocating. I don't want any of the technical information removed. I actually commend your commitment to accuracy and precision and agree with you that popular science publications are often very misleading in their summaries! But just because a good summary is very difficult to write does not mean it shouldn't be attempted. What would be so bad about leaving all the technical information, but including a few sections of more accessible summary (especially in the opening)? I must say I am definitely not in the wrong article; ALL Wikipedia articles should be written so that a general, literate audience can understand them. That's Wikipedia's policy. Take a look at the article on quantum mechanics, for example. It's an article that many brillant scientists have contributed to over the years. In some sections, it has language as simple as this: "Many electronic devices operate under effect of quantum tunneling. It even exists in the simple light switch. The switch would not work if electrons could not quantum tunnel. . ." Now. . .is that inaccurate? Maybe I'm wrong, but I think if that article can contain passages that are that simple then so can this article (even if they are quite hard to write). Becca (talk) 20:47, 10 November 2017 (UTC)

Footnote of lead image.

It reads: "These are five of the infinitely many paths available for a particle to move from point A at time t to point B at time t’(>t). Paths which self-intersect or go backwards in time are not allowed."

Surely it's meant to say that paths which go backwards are not allowed, which could be a corollary of the non-intersection axiom. Otherwise it suggests something related to time travel.--TZubiri (talk) 04:03, 18 October 2020 (UTC)

I gather it is trying to exclude going backwards, e.g. S-curves. "In time" is a metaphor for antiparticles. Cuzkatzimhut (talk) 20:44, 18 October 2020 (UTC)

Poor article, we need a better formulation

The article does not define what the Path Integral is. Most of the text is irrelevant for the subject. Some text is directly wrong. For example the statement "The Lagrangian is a Lorentz scalar, while the Hamiltonian is the time component of a four-vector" is not true: both the Lagrangian and the Hamiltonian are SCALARS, being sum or difference of potential / kinetic energy. (The relation of the Hamiltonian to four-vector is true, but both are scalars nevertheless). Whatever, the distinction is not relevant here. 194.132.237.154 (talk) 11:33, 28 November 2024 (UTC)