Talk:Variational principle

I don't see how this is any different from the Euler-Lagrange formalism or action principle. The bottom half of the article is even about some approximation method, which seems completely out of place. --MarSch 13:34, 22 Jun 2005 (UTC)

Hi MarSch. For me, the variational principle is indeed simply the principle of least action, but written out for a hamiltonian and electronic system as described in quantum chemistry (as in the section I added). I don't know of any other meaning, especially in pure physics. I think the article needs to be reorganized, the introduction restated. I was planning to do that some time ago, but lacked the time. Karol 20:30, Jun 22, 2005 (UTC)

The approximation method I was referring to is the variational method. Does it have anything to do with the principle of stationary action? It is claimed in that article, but not explained. --MarSch 10:02, 23 Jun 2005 (UTC)

The source of the confusion here seems to be the various different uses of the term 'variational principle'. This article has a list of rather unrelated things that could possibly be called variational principles, and then a decent description of one particular example. The variational principle (or variational theorem) in quantum mechanics is not an approximation method, is not out of place, and is exactly the basis of the variational method in quantum mechanics.

Merge with Calculus of Variations?

Should this article be merged with the calculus of variations page? It seems like this page only details some basic applications to the calculus of variations and explains some general aims of the calculus of variations. The C of V page could use a better explanation on its overall aims. --69.180.18.247 14:42, 4 September 2006 (UTC)

The Poincare group is not a gauge group. 141.34.68.221 (talk) 12:38, 15 August 2008 (UTC)

Should Variational principle#Variational principle in quantum mechanics be merged into Variational method (quantum mechanics)?

The "variational principle" of this section is the statement that the expectation value of the energy of a quantum system in any state is greater than or equal to the ground state energy; it is the base of the variational method. I don't think it is too relevant in an article about variational principles such as the principle of least action and similar ones. So I'd rather move that section to the "Variational method (quantum mechanics)" article. (BTW, I'd also omit the proof: it isn't something that astounding and Wikipedia is not a textbook.) What do you think? --A. di M. – 2009 Great Wikipedia Dramaout 12:10, 18 July 2009 (UTC)

By and large I would leave proofs in the article (particularly simple ones). It helps understanding, and is part of what a comprehensive article should cover, to see where a result has come from.

My understanding is that WP:NOTTEXTBOOK is primarily about prose style, not about the scope of content.

As for content, it might well be worth also relating it (and vice-versa) to the more general mathematical setting laid out at Calculus_of_variations#Sturm-Liouville_problems.

I see we also have further articles on Ritz method and Rayleigh-Ritz method, both of which could also use some attention. Jheald (talk) 19:28, 18 July 2009 (UTC)

Seems to me also that almost every statement in the lead here is pretty dubious, or at least needs more input to be understandable. The whole article is not good. Jheald (talk) 19:38, 18 July 2009 (UTC)

Yes, it is quite in bad shape. Back to the original question: do you agree that the section "Variational principle in quantum mechanics" would be more useful in "Variational method" than here? If no-one objects, I'm going to move it there. --A. di M. – 2009 Great Wikipedia Dramaout 13:34, 19 July 2009 (UTC)

I came here to find out what the Variational Principle was, and this article was no help whatsoever. The article on the History of variational principles in physics is better. This article should be merged into Variational method (quantum mechanics) and replaced by a merger with the History article. A B McDonald (talk) 16:32, 19 April 2010 (UTC)

• Merge done V8rik (talk) 19:48, 4 January 2012 (UTC)

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What is it with self-adjoint operators?

The article mentions “Any physical law which can be expressed as a variational principle describes a self-adjoint operator.” with a reference to Lanczos' The Variational Principles of Mechanics. What does it mean for a principle to describe an operator? I briefly read through Lanczos' book and didn't find any mention of this anywhere, but the fact that no page or chapter is mentioned in the citation doesn't really help. Michal Grňo (talk) 14:31, 17 August 2020 (UTC)

Merge with Stationary-action principle?

This page is weak and stationary action principle is weak. They should be merged, under "Action principle" Johnjbarton (talk) 23:09, 13 November 2023 (UTC)

It is not the same as "action principle", it is more general. At best we could merge stationary action principle here but I would prefer if we did not, or merge Variational principle with calculus of variations. Action principles have always been for me for mechanics and dynamics, while variational calculus in general covers the action principles, other physics methods that do not minimize an action like Ritz method or variational method (quantum mechanics) and non physics stuff like the ones listed in "Examples".--ReyHahn (talk) 08:14, 22 November 2023 (UTC)

I agree. Johnjbarton (talk) 16:51, 22 November 2023 (UTC)

create page: variational logicism because even neologicism is single-logic biased

Variational logicism (or variant logicism) means that infinite logical foundations are possible. It's based on the term variety and not on the mathematical term variational but it doesn't exclude it. The axiomatic system of all axiomatic systems doesn't exist because mutually exclusive axiomatic systems are logically possible (the omniaxiomatics doesn't exist = the universal axiomatics doesn't exist). Also the set of all sets doesn't exist (if we accepted a stationary = set pseudoomniaxiomaticity = a set of all axiomatic systems which doesn't actively engage their logic as a true axiomatic system). Neologicists supposedly wanted to remove the biases of logicists, but actually most of them erroneously claim that a single fundamental/foundational logic is possible; which is proven to be wrong, because logic is always axiomatic and contextual, but infinite axiomatic systems are logically possible (list-based, algorithmic, programs and hybrid axiomatics) and infinite logical contexts. Variational logicism accepts the fact that logic is rule-based, but the rules can vary per axiomatic system or other logical context. Infinite axiomatic systems are logically possible. We can experiment by creating axiomatic systems. Most axiomatic systems are weird and useless. Some axiomatic systems are allomathematics = mathematics (proof systems) of different axiomaticity/ axiomatic foundations. Some axiomatic systems are substantiality axiomatics = physioaxiomatics = physical axiomatics = physical foundations (the quantum foundations is the foundations of our universe). The physical axiomatics have to be more logically coherent = with more self-engaged foundations than the proof-system axiomatics, but they don't have to be as crystal clear as the proof-system (mathematical) axiomatics. The axioms of mathematics don't originate from a single logical kernel and according to the foundations of mathematics they aren't maximally coherent (they are eclectic; see: eclecticism). The axioms of mathematics aren't a physical foundations; they would disperse without causing a universe. Proof systems and universes don't have the same foundations. Both 1. mathematics and the infinite allomathematics and 2. the infinite universes are logical systems based on logical foundations, but that doesn't mean they have the same foundations. Informational entropy and thermodynamic entropy are intertwined in the physical foundations. The "axiomatic prerequisites of the physical foundations" is a field of study hypernymic/hypernymous/superordinate to the quantum foundations which is about our own universe. The infinite alternative physical foundations of the infinite logically achievable universes don't have strictly common rules because the axiomatic system of all axiomatic systems doesn't exist, but still we can postulate some basic prerequisites. 2A02:2149:8B83:6500:9464:BD1F:2B81:D064 (talk) 01:52, 3 April 2024 (UTC)