Talk:Renormalization group

Rewrite

At last I was able to rewrite completely the article. Of course, it is only a draft and needs lots of improvements. I'm preparing myself some more pictures. Sorry I forgot to sign and add summary of changes! Javirl 14:20, 2 November 2005 (UTC)

I find this article lacks a guide. Sometimes it goes into too much technical detail in math and sometimes leaves things too vague. I think this article should be split into parts. In the first one the very idea should be explained, mostly Kadanoff blocking with pics. The second one should be for RGT, fixed points, relevant-irrelev.-marginal operators, the semigroup character and universality classes. As a third one, although historically it might have come first, I'd add renormalized perturbation theory: Callan-Symanzik and applications to particle physics. Then, links to more specific techniques: Real Space RG (BRG, DMRG...), Momentum Space RG (diagrammatic, exact RG), RPT... and finally a section on the history of RG techniques. As addenda, other topics may be mentioned: relation to fractals, conformal field theory, etc. If nobody is opposed, I'll put my hands to this in a few days. Javirl 16:24, 20 September 2005 (UTC)

What is an "infrared attractor"? Not found via google.... NealMcB 00:30, 2004 Jan 22 (UTC)

No, I've never heard these terms either. Nor can Google find "infrared repellor". However, the term infrared fixed point does appear many times. See http://www.lns.cornell.edu/spr/1999-08/msg0017563.html for a reference. Also, ultraviolet fixed point. -- The Anome 07:54, 14 May 2004 (UTC)

I doubt that the characterization of 'attractor' and 'repellor' are correct. You get a continuum limit if you have an ultraviolet fixed point. The critical point of a statistical field theory corresponds to an infrared fixed point. Each phase is controlled by an attractive fixed point in it, which is usually an infrared fixed point and corresponds to homogeneity and trivial correlations. Critical points are always unstable in at least one direction.

The article is atrocious in its present state. I'll come in for a cleanup soon. — Miguel 14:34, 2004 May 25 (UTC)

I have redirected renormalization to this page. This was the content of the renormalization stub article:

A method of removing singularities from certain calculations in quantum mechanics. See also Renormalization group.

— Miguel 07:27, 2004 May 28 (UTC)

Hmmm... seems like there really should be a separate article on renormalization itself, maybe focusing more on techniques in diagrammatic QFT. It seems odd that the article attributes the notion of renormalization to Gell-Mann and Low; they were more associated with the renormalization group, right? Renormalization goes back at least to Schwinger, Feynman and Tomonaga, though they may not have fully realized what they were dealing with prior to the renormalization group concept. --Matt McIrvin 03:06, 3 Oct 2004 (UTC)

I seem to recall that there are also a couple of Russians who wrote on the renormalization group before Gell-Mann and Low, but were not credited in the West until much, much later. I can't remember the names of the Russian physicists, nor have I been able to track down this bit of trivia. If I had to guess I'd say that Bogoliubov must have been one of them, but I might be wrong. — Miguel 08:15, 2004 Oct 4 (UTC)

It was Bogoliubov and Shirkov. I'll see if I can find the reference. -- CYD

Shirkov gives the references in his overview, which I added as a reference. He also mentions Petermann and Stückelmann as the first to bring in the whole group idea. -- sebastianlutz

The link to the beta function wrongly points to the mathematical Euler beta function. This is NOT what is called the beta function in RG. There the beta function describes the change of the coupling constant(s) with the scale parameter. -- CBL

This article is so poorly written one wonders if the contributors even understand what they are talking about. Junk it and start from scratch..... — Preceding unsigned comment added by 64.105.137.249 (talk) 05:47, 31 December 2011 (UTC)

Relevant and irrelevant operators, universality classes

From this section it follows that for example temperature, pressure and volume are relevant observables. Translating back to the RG behaviour the magnitude of these observables is supposed to increase as the observed scale is increased. I don't see what that is supposed to mean. Perhaps someone could elaborate on this? --MarSch 12:27, 4 May 2006 (UTC)

I removed a line about the number of microscopic interactions being of order 10^{-23}. Presumably, the editor who wrote this was thinking about atoms in a box. However, RG flow is relevant in many physical contexts; in most relativistic quantum field theories for example and this statement is not accurate there. I also added a line explaining why we see only particles of spin 0, 1/2 and 1 at low energies. cheers, Perusnarpk (talk) 21:40, 30 July 2008 (UTC)

User:R.e.b. re-inserted the statement about there being 10^{-23} microscopic interactions. This is incorrect, hence I've removed the statement again. Please do not re-insert without justifying it here. Second, I've elaborated the explanation of why we see only particles of spin less than 1 at low energies. The idea I am trying to express is that the standard model is an effective field theory, just like other quantum field theories. Since, the interactions of particles with spin larger than 1 are necessarily irrelevant, we do not see these particles in a low energy effective theory. In a `theory of everything' like string theory, these particles are indeed predicted at high energies, of order, the string scale, but they decouple at observable energies. If my explanation is not clear, please refine or discuss here. 202.159.224.74 (talk) 08:42, 10 August 2008 (UTC)

Perturbation expansion

This statement, that I suspect is incorrect,is from the Momentum Space RG section

Momentum-space RG is usually performed on a perturbation expansion (i.e., approximation). The validity of such an expansion is predicated upon the true physics of our system being close to that of a free field system.

Please confirm that this indeed wrong or please elaborate on the details if it happens to be true. As far as I understand, the validity of any perturbation rests on the convergence properties of the perturbative series.

Elements of RG theory

Shouldn't RG rather be a monoid, since a 1-element exists and semigroup is (not always, but often — and as well @wikipedia) defined without 1-element? --CHamul 10:24, 14 November 2006 (UTC)

Too technical

Unfortunately, this article does a poor job of explaining RG in a context independent of any particular application. Notably missing from it is any mention of RG in Chaos/Complexity theory, where it is critically important in Feigenbaum's proof of universality for a class of functions giving rise to chaos under a period doubling route. The article also reads -- as do many Wikipedia articles on technical topics -- like it is intended for specialists (though I wouldn't know why they would want to read it), as it contains impenetrable references to a raft of other things that were defined elsewhere. Article authors need to recognize that non-specialists turn to Wikipedia for definitions, and that the articles like this are of poor quality unless they are intelligible to someone not immersed in the field. —Preceding unsigned comment added by 98.228.35.247 (talk) 20:21, 21 November 2010 (UTC)

Amen. David Spector (talk) 02:54, 4 March 2011 (UTC)

I agree with this comment. There should be description of RG in the context of perturbed ordinary differential equations, which are often studied in the field of dynamical systems. Current version assumes some knowledge of quantum field theory, but the RG is more general concept and hence will have wider readership. NorioTakemoto (talk) 07:50, 9 November 2024 (UTC)

Group?

I have a question. The article speaks about the "renormalization group", but nowhere does the article prove that there is a structure that forms a group. Is the renormalization group a group, or is it just another bad name in Physics? I study Physics. But the mathematical definitions tend to be a lot better, in the sense that they mean what one expects them to mean. In this case, I feel there is something I am not getting, because I don´t see what the group is and if it is useful to think of transformations in this way. So, is there a group hidden there, or is better to ignore the name and just read the article? --190.188.2.122 (talk) 01:16, 17 February 2011 (UTC)

I am not sure, but I think that the group is the group of scale transformations — making the small things larger with corresponding changes in the charges, masses, and coupling constants. It has an identity element — leaving all the distances, time durations, charges, masses, and constants the same. An inverse transformation would just reverse all the changes. The group operation is composition of two transformations to give the composite transformation, e.g. doubling distances and trebling distances combine to form multiplying distances by six. Does anyone know if this is correct? JRSpriggs (talk) 06:25, 17 February 2011 (UTC)

The article makes the point that "there need not be an inverse for a given RG transformation. Thus, the renormalization group is in fact a semigroup." I think JRSpriggs is exactly right that the "group" in "renormalization group" refers to the set of scale transformations, except for the fact that they don't have inverses (the same low energy/long distance physics can result from many different underlying high energy/small distance theories) so renormalization group is really a (slight) misnomer. Mattysb (talk) 13:54, 21 February 2011 (UTC)

To Mattysb: Thank you for clarifying that. JRSpriggs (talk) 02:58, 22 February 2011 (UTC)

Regarding group properties: Shankar (http://arxiv.org/abs/cond-mat/9307009) has a short discussion on this issue. As far as I know the RG is a semigroup since the inverse element does not necessarily exist - this was stated earlier in this discussion. —Preceding unsigned comment added by 155.69.182.225 (talk) 13:21, 22 March 2011 (UTC)

Throughout the article, "RG" is used ambiguously, albeit in comportance with established and immutable physics practice. "RG", in fact, refers to both "renormalization structure", the Wilsonian vision of mutation across scales; and also the "renormalization group trajectory", a bona fide group, indeed a Flow (mathematics), with an identity and an inverse, for renormalizable theories — admittedly a small subset of theories, but nevertheless the ones studied first, best, and with the most standard results taught first. In this latter case, a system such as QED may be evolved forward and backwards, and the variation of its coupling monitored and compared. I would recommend leaving things as they are, but still making perfunctory efforts to implicitly contrast the group with a unique RG trajectory, to the grand multidimensional flows of the Wilsonian scheme. Cuzkatzimhut (talk) 21:06, 27 March 2011 (UTC)

Connection to group theory needed

I consider myself quite familiar with elementary group theory, but even I can't understand the relation of this object with the mathematical notion of a group. From the above discussion, I gather that this is an abuse of terminology. If so, that has to be clarified.--Jasper Deng (talk) 07:17, 11 August 2017 (UTC)

I think mathematical types are grossly overthinking this. The RG is a group as a flow, as stated above, and the 2nd boxed equation of the article displays the group composition law involved, albeit trivial. It is translating on a scale line, and hardly anything else, $T_{\mu /M}~T_{\kappa /\mu }=T_{\kappa /M}$. It manifestly has the evident identity and the evident inverse. Expecting an elaborate group structure beyond sliding on a dumb infinite line is spectacularly misplaced; but mathematically inclined readers return to the "scene of the crime" again and yet again. People do sometimes abuse notation by referring to the semigroup in some implementations of this procedure, where the inverse is hard to pin down, but the prototype they abuse is the structure displayed, and the inverse is aspirational. In that sense, "RG" signals all the techniques employed to work out the group composition law: it's just a tag.

I'm not sure what couple of words in a footnote would get them off the back of the article, but you might suggest some. Cuzkatzimhut (talk) 14:34, 11 August 2017 (UTC)

"spectacularly misplaced" - can you AGF just a bit more? How does the second box yield a group composition law? I understand that scale transformations already possess the properties of associativity and identity (like any collection of functions from a set to itself that include the identity function), however those just tell me this is a monoid, not a group. I'd like more clarification of where the additional property of inverses comes in in the article, as the above statement about a semigroup is sourced and would seem to contradict your assertion.--Jasper Deng (talk) 18:23, 11 August 2017 (UTC)

Apologies for perceived tactlessness, but, of course, I do still feel strongly about the needless storm in a teacup. I repeat, this is mere discussion of translations on a line: Array M, μ, κ at three points of a line. Translation from M, to μ, and from μ to κ amounts to translation from M to κ. Translation from μ to κ, may return to μ via translation from κ to μ. There are no requirements in this Schroeder equivalence equation discriminating between forwards and backwards flow.

The semigroup drivel refers to practical calculations in restricted (Wilsonian) settings where this motion is practical to calculate from short distances to long ones, but, in general, the real beast that Gell-Mann and Low found the solution for is perfectly invertible, a feature of renormalizable theories. It is true, that lots of calculators are moored in their particular parochial context and "don't mean this--this is trivial... instead, they mean...noninvertible RG transformations... so Group is a misnomer". So RG is a sloppy tag of the context they find themselves in, here "in such lossy systems". But the RG is a bland line.

This illustrates my concern that misplaced concerns will insinuate misconceptions, even through the diffident wording, sourcing and all, and obscure the essence of the procedure. Cuzkatzimhut (talk) 19:09, 11 August 2017 (UTC)

An article about a (purported) group is gonna attract mathematician readers as well. Sloppy wording like the restricted case you mention should be explicitly declared to be such. More to the point, as a reader, I shouldn't be having to ask for an explanation of this. If it is "mere discussion of translations on a line", then we absolutely do not need to hide it under extremely technical jargon that currently comprises the lede of the article.--Jasper Deng (talk) 21:14, 11 August 2017 (UTC)

My point exactly. The group structure is a non-issue. By contrast, the self-similarity feature on that line is subtle and sublime, and over 3 Nobel prizes were awarded to those who fleshed out the details. If it is the name that attracts readers, well, that's grim. Cuzkatzimhut (talk) 22:40, 11 August 2017 (UTC)

"a non-issue" - if it were a non-issue, then I would not be bringing it up here. It may be not the main point of this article but the article is not complete or accessible without it.--Jasper Deng (talk) 01:00, 12 August 2017 (UTC)

I think what irritates mathematians and mathematically inclined physicists about the naming is not that they “overthink things“, but that the language common in this field implies there being a mathematical object called “the renormalisation group”, and that the way to understand what's meant by “RG this” and “RG that”, is to first understand this object (As puzzling this attitude might seem to mathematically non-inclined physicists!). I slightly edited the first sentence to avoid giving this impression.

As an aside, i think more could/should be said about how exactly the name is a misnomer, including a more abstract perspective on RG topics that highlights the mathematical structures actually characteristic of what “RG” is, but that should propably be written by an expert on the topic, not by me. --88.68.128.13 (talk) 13:33, 3 June 2020 (UTC)

I believe, I know!, any further discussion of trivial scale translations in terms of group theory, somehow hoping that group theory would thus shed more light on RG, a mere term for a technical picture, is merely barking up the wrong tree. If one were confused about RG, it is certainly not for lack of mathematically precise background! It is the one dimensional translation group, and hardly anything else. More, rather than less discussion, beyond a footnote to the confusable, amounts to virtually changing the subject, and would frustrate students seeking to get to the point by distracting them to aggressively irrelevant tangents. Cuzkatzimhut (talk) 14:25, 3 June 2020 (UTC)

Physical Predictions

It would be nice if the anonymous 178.197.254.3 editor discussed the object of his persistent edits reverted by JRSpriggs, soundly, in my opinion. Gell-Mann and Low, in the reference cited, went beyond formal solution of the finite renormalization group equation to an expression equivalent to the rise of the QED coupling with energy precisely as quoted in the LEP measurement. Beyond mainstream professional opinion, Prof Harald Fritzsch stakes his professional opinion on it, in print (would 178.197.254.3 require the specific citation? DOI:10.1142/S0217751X10049864). Do S & P do so in the papers quoted, in such specificity? Do B & S? Is the paternity of this type fo prediction contested? Please discuss, before tendentious repetitive repartee edits! Cuzkatzimhut (talk) 20:35, 1 May 2011 (UTC)

Remarks

The History section is quite messy and sometimes incorrect. For example, Λ_QCD is not the value of the RG scale μ at which the coupling diverges, that is the Landau pole. Λ_QCD is the value of μ at which the coupling reaches the value 1. This means that perturbation theory is no longer reliable for energy values below Λ_QCD. — Preceding unsigned comment added by Swoun (talk • contribs) 15:42, 24 February 2014 (UTC)

Well, yes and no. Λ_QCD is the value for μ at which the argument of the logarithm in the denominator of the one-loop integrated β-function result becomes 1. The logarithm thus vanishes, and the naive one-loop perturbative coupling blows up, so it cannot be construed as small. I don't know how you propose to clarify this, but since no mention of the confinement scale was made, I don't see any confusion, unless the reader asked for trouble. Besides, this is not a pedagogical intro to the renormalization group: it is only a breezy historical exposition section.

Of course, if and when you had a superior expository section later on, with plenty of opportunities to clarify things, like providing the trivial integrated one loop result itself, extraneous context on Λ_QCD could wait until then, and move from the history section, as it would demonstrate its role by inspection. Cuzkatzimhut (talk) 20:31, 24 February 2014 (UTC)

There is a problem of terminology. The solution to the beta function equation for the QCD coupling at one loop order is given by:

$g={\frac {1}{1+k\log(\mu /\Lambda )}}$

The integration constant Λ is what I called the QCD scale Λ_QCD. If you rewrite the solution as:

$g={\frac {1}{k\log(\mu /\mu _{0})}}$

the integration constant μ₀ is not what I called the QCD scale, but rather the Landau pole. Note that perturbative QCD (g < 1) is valid only for μ > Λ and not for μ > μ₀. In particular, it is not valid for μ in the range Λ > μ > μ₀ . This gives the meaning to Λ. Note also that a coupling constant is said to be strong, not only when it diverges, but if it is equal to or larger than 1. The notion of Λ is in this way more fundamental and there is no name to it in your terminology. If you are using references such as Peskin and Schroeder, they reserve the name Landau pole to a high-energy pole and call Λ_QCD to a low-energy pole in asymptotically free theories. They ignore the important meaning of the above Λ. The fact that the QCD coupling blows up at some energy is not physically meaningful. The fact that it is 1 at some energy is meaningful: perturbation theory is no longer reliable (and therefore we should not even cross to the regime of energies where g > 1). Swoun (talk) 01:13, 26 February 2014 (UTC)

Anything and everything is fine as long as the formulas utilized are stated. That's why shadow-boxing on unwritten definitions is counterproductive. The first integrated answer you provide is automatically and routinely if not universally rewritten as the second, and then the μ₀ is determined from data fits, avoiding silly complications and clutter.

I am just utilizing the mainstream definition, $\Lambda _{QCD}=\mu \exp(-1/(kg(\mu ))$, in your notation, along with thousands.To avoid arid theological discussions like this, most modern practitioners normalize the first formula with a suitable number in the denominator and the Z mass instead of Λ , M_Z, so the strong coupling is pegged to its value at the Z mass. In perturbation theory, 1 and ∞ are comparably useless, and nobody contemplates close values.

If you felt that strongly about the notation of formula 1, you might go to the suitable wikis linked, and on dimensional transmutation, asymptotic freedom, etc... or the Landau pole, and tweak/expand/discuss those. My sense is to leave this history section alone and do all the deconstruction you want in the specialized technical wikis. Arguing about invisible formulas here cannot help a reader. I would strongly urge you, in this task, to stick to the conventions of the users in the field, so the Particle Data Booklet definitions, cf this] or this. Cuzkatzimhut (talk) 11:56, 26 February 2014 (UTC)

More information needed

Links to "universality class" redirect here. This article gets as far as mentioning that universality classes exist, and then abruptly stops. To be complete, it really needs to contain some kind of technical explanation of what they are and how they arise. (Though I do agree with earlier comments that the article is way too technical, in the sense of being completely inaccessible to the kind of person who needs it most.) 240F:7C:FC1A:1:1003:C899:842E:E0A (talk) 10:26, 17 December 2014 (UTC)

So, then, what exactly are you proposing to insert? How do you explain something as technical without technical concepts?

Can you explain functors without math? Cuzkatzimhut (talk) 15:32, 17 December 2014 (UTC)

I'm proposing to insert additional technical information, while also agreeing with earlier comments that say the technical information currently included needs to be presented in a *much* more accessible fashion. (Or rather, I'm proposing that someone else insert the required additional technical information. It was what I was hoping to find when I came here.) 131.112.112.6 (talk) 05:28, 19 December 2014 (UTC)

Go ahead. WP is a collaborative pursuit. Propose it here first. Cuzkatzimhut (talk) 11:21, 19 December 2014 (UTC)

To repeat my parenthetical comment: I'm proposing that someone else insert the required additional technical information. I can't do it because I don't know that information. It was what I was hoping to find when I came here. If you're not in a position to make the suggested improvements then this comment is not aimed at you. 240F:7C:FC1A:1:D50E:E423:8FA7:F411 (talk) 01:33, 20 December 2014 (UTC)

You evidently came to the wrong place. You probably wish to be briefed on critical exponents for which there is a link, and not waste time thrashing around chaos and RG. In any case, I hyperlinked the standard Zinn-Justin reference in Scholarpedia. My insistent point, however, is that the place for a nontechnical introduction to basins of attraction and critical exponent calculation and reduced surfaces is definitely not here---unless you think you can contribute something that others have wisely skipped. It would be hard work to vulgarize the Scholarpedia article for the math-avoidant crowd. Do due diligence and read up. Cuzkatzimhut (talk) 21:17, 26 December 2014 (UTC)

Overlap with "Universality (dynamical systems)"

There is another article, Universality (dynamical systems), that seems to cover some of the same ground as this one when it comes to universality classes. Perhaps they should be merged, or at least more systematically linked to one another. Unfortunately the other article suffers from the same problem as this one regarding universality classes, in that it's purely descriptive, lacking technical information about what universality classes actually are and why they have the properties they do. 240F:7C:FC1A:1:D50E:E423:8FA7:F411 (talk) 01:49, 20 December 2014 (UTC)

Problem with the boxed equations while generating the pdf version of the page

I have noticed that the "Equation box" prevent the equations from being written in the pdf rendering of the page. I would suggest to remove them, or to find a different way to highlight them, which is compatible with the pdf creation. --Oakwood (talk) 02:26, 16 June 2015 (UTC)

I would disagree: box templates highlight important equations. I don't disagree that something snags with these specific eqns at present as rendered in the pdf, which normally does not happen to other articles with boxed equations. In fact, for printing, all equations, including unboxed ones, suffer/disappear. A pdf version off the printed version should be acceptable? I am guessing your might be using a nonstandard platform?

You may have discovered a bug (see Wikipedia:Bug reports and feature requests). I suggest investigating the problem by first going through all the rendering options in your WP settings, preferences>appearance>math (PNG, Mathjax, etc...), reporting to the suitable technical pages, and seeking a general fix. (This is not the only pathology of the pdf-rendering script, as I assume you have noticed the formula overflow mayhem in section 6 of the very same article, when you render it to pdf this way!! ---a problem "print > save as pdf" lacks.) It is a fact that the PNG or MathJax choice allows printing the article with the boxes visible in the printer friendly version, which can then be saved as pdf instead of sending to a printer; you may also convert to pdf your versions of yesterday, off the article's history. You might also experiment with alternate box templates, and/or eqn formatting... But some type of highlighting beyond your quick fix may be desirable, as the formula overflow in section 6 persists. Cuzkatzimhut (talk) 10:22, 16 June 2015 (UTC)

Gratuitous repeated removal of Ken Wilson's portrait

Pls see Talk:Quantum field theory#Gratuitous removal of Ken Wilson's portrait. The fact that KGW is the one pioneer in the history of physics shaping the RG is not a matter of dispute, one hopes! Cuzkatzimhut (talk) 14:38, 1 March 2017 (UTC)

I'm not sure which event you are talking about, but the history of this page suggests that copyright may have been the issue here. Certain people watch like hawks to see if they can find something to remove. In one case our lab photographer had to agree personally that the photo he had taken could be used, it being deemed insufficient for the dept. to give formal assent. Fortunately he was still working at the lab and could give assent, but if he had retired that photo could not have been used! There was also a case of the reverse, where someone replaced the photos on a WP page by his own distinctly inferior ones, against the wishes of the photographees. Fortunately he was persuaded to abandon his project and restore the originals. --Brian Josephson (talk) 11:00, 5 September 2017 (UTC)

You might track the history down from the dates, May of this year, and especially the editing history of Ken Wilson's article. [Ticket#2017032910014224]. Prof Paul Ginsparg of Cornell provided ample approvals form the Physics Dept owning the pics, but, because they had appeared in the media during Wilson's Nobel prize celebration, the Wikimedia permissions' watchdogs were not satisfied. As a result the wold can easily find public domain pics of KGK through google image, but not through Wikipedia! Cuzkatzimhut (talk) 15:30, 5 September 2017 (UTC)

Recent "too technical" template

Incontrovertibly an invitation to WP:OVERSIMPLIFY... Lies to children... Of course the article is technical: it is the heart of quantum field theory. The relativity article and the Poincare group article and the QM mech articles are technical too to the novice, but it is absurd to pretend this is not unavoidable. 95% of mathematical articles here are too technical. Physicists start appreciating the RG after 4-5 years of technical schooling, and arguably fully master it after 20. Hopefully the template will add a few short words to the outsider, but, if the experience of several articles in WP is a guide, this appears like the beginning of a streak of uncontrolled erosion. More and more vapid nitpicking qualifying weasel words are added, which signal to crowds of fussing outsiders to come in and sculpt the narrative, and the end result is massive defocussing and detraction form the main "message" of the article, usually relegated to the end, and parts of the narrative the perpetrators normally decouple from. This is the routine progression of philosopher- and historian-infested articles like the Uncertainty principle, for instance, where regularly the focus is eroded in favor of lies-to-children bloviation---until a brave soul removes the underbrush in a spasm of righteousness. This repetitive drama seriously compromises the quality and reliability of WP. Cuzkatzimhut (talk) 15:22, 11 August 2017 (UTC)

Nevertheless, I'm sure the article can be made more readable without sigificant oversimplification. For example, a possibility that occurs to me as I read it is that the technical comment on conformal transformations near the start could be moved to a footnote.--Brian Josephson (talk) 09:44, 5 September 2017 (UTC)

You mean in the 2nd paragraph? Absolutely! Of course there is room for thoughtful improvement.Cuzkatzimhut (talk) 10:40, 5 September 2017 (UTC)

Yes. But I agree with your general point, and hence with your point of view that the article is not too technical, in the sense that it is only as technical as it needs to be to be useful in the way that an encyclopedia ought to be. The situation may be compared with that of the Stanford Encyclopedia of Philosophy, which has articles that are pretty technical, as they need to be in order to enlighten readers.
I guess the w'pedia procedure at this point would be to gather consensus. If no one argues convincingly for a reduction in technicality then maybe that template can legitimately be removed. --Brian Josephson (talk) 10:50, 5 September 2017 (UTC)

I would argue for the template to go, but not ardently. There could be contributors with preternatural communications skills who might be able to improve it, and, even though it lends the article an aura of a construction site, at least warns/scares-off the self-declared "gifted amateur" who wonders why they don't get it, past the lede. It's one of the deepest and most fundamental theories of theoretical physics, and expecting any quick-and-easy explanation in a couple of pages may simply not be possible. The grim history of the Uncertainty principle might illustrate what happens when readers get to expect that, or else... Cuzkatzimhut (talk) 15:23, 5 September 2017 (UTC)

There are not-so-few editors who feel that physics articles should primarily be expressed in "ordinary language". They'd argue that one loses most of the audience if the article goes technical. The problem with insisting on this approach is that an article will go from having, say, 5% of readers (assumed unfamiliar with the topic) understanding it into having 0% of readers actually understanding it, while the number of readers that believe they understand it go up substantially. Understanding single words, and even complete sentences doesn't mean understanding the message (or physics).

That said, physics culture (physicists absolutely refuse to define notions precisely unless perhaps at the threat of withdrawn morning coffee for a month) can certainly be perceived impenetrable. For instance, I'd like to see "length scale" and "energy scale" defined precisely. This might not be easy as textbooks offer hand-waving only, usually with reference to other undefined notions (it is supposed to be obvious what is meant). Note that this is an argument for more technicalities, not fewer, and also for less jargon. YohanN7 (talk) 12:26, 7 September 2017 (UTC)

For the record, though it may be five years late, "length scale" and "energy scale" generally the "natural units" of a system. To be formally precise: It is not generally meaningful to talk about a function of a dimensional quantity (a quantity with a unit like seconds), because we usually define such functions based on power series but it is meaningless to add 1s + 1s^2, for example. Fortunately -- or, arguably, as a direct consequence -- the laws of nature inevitably divide out all such quantities by a characteristic "natural unit" before actually using them in calculations. It is quite common to see an equation that, say, only ever depends on a ratio x/x₀, where both x and x₀ are lengths, and never on a bare x alone. In such a case, we would then refer to the quantity x₀ as the "natural length scale" of the system. The most famous examples of such natural units are the Planck units, which are the natural scales of the Standard Model and general relativity as a whole, but smaller subsystems and theoretical models have their own characteristic scales. Linkhyrule5 (talk) 23:56, 8 April 2023 (UTC)

I removed the template as it is no different from other similar physics entries, and there is clarity when one stops at the lede. Nonexperts should not complain for parts beyond the introductory sections. So it looks like the complaint is at the physics level on wikipedia, not this article. Maybe the solution is simplified Wikipedia. Limit-theorem (talk) 14:05, 22 March 2018 (UTC)

Good move. My impression is that several of these templates represent the frustration of an unclued reader who feels like shaking his fist at a field. As a participant of a Physics questions website, I can attest to the broad satisfaction of the bulk of physics students with WP physics coverage, in some contrast to standard textbooks! I think an editor with salutary ideas needs no prompting by a template: she or he knows a sentence or a paragraph or a section is improvable. Cuzkatzimhut (talk) 22:24, 23 March 2018 (UTC)

The down-fall of physics

Electrons consisting of electrons(??????), positrons and photons. Bare electrons, dressed electrons, clothed electrons? It feels like someone is cheating here. Bad article ... again!!! — Preceding unsigned comment added by Koitus~nlwiki (talk • contribs) 20:47, 26 October 2020 (UTC)

Inconsistencies

It is misleading to invoke the Avogadro number. The model space is something different and in principle can be much larger. For instance, the number of different chemical compounds consisting of C and H atoms grows more than exponentially with the number of atoms.

It is misleading to say that a relevant parameter "always grows". In what direction? In respect to what sign convention? Relevance, irrelevance and marginality describe the behavior in the vicinity of a fixed point.radical_in_all_things (talk) 17:10, 15 November 2021 (UTC)

Nature focus issue (Nov 2023)

https://www.nature.com/collections/jbhcdccded Maybe cite. 2601:644:8501:AAF0:0:0:0:2034 (talk) 00:35, 28 January 2024 (UTC)

Mathematical notation

One line of this article is this:

${\frac {d}{d\Lambda }}S_{\operatorname {int} \Lambda }={\frac {1}{2}}{\frac {\delta S_{\operatorname {int} \Lambda }}{\delta \varphi }}\cdot \left({\frac {d}{d\Lambda }}R_{\Lambda }^{-1}\right)\cdot {\frac {\delta S_{\operatorname {int} \Lambda }}{\delta \varphi }}-{\frac {1}{2}}\operatorname {Tr} \left[{\frac {\delta ^{2}S_{\operatorname {int} \Lambda }}{\delta \varphi \,\delta \varphi }}\cdot R_{\Lambda }^{-1}\right].$

Is there some possibility that it was actually intended to by the following?

${\frac {d}{d\Lambda }}S_{\operatorname {int} \Lambda }={\frac {1}{2}}{\frac {\delta S_{\operatorname {int} \Lambda }}{\delta \varphi }}\cdot \left({\frac {d}{d\Lambda }}R_{\Lambda }^{-1}\right)\cdot {\frac {\delta S_{\operatorname {int} \Lambda }}{\delta \varphi }}-{\frac {1}{2}}\operatorname {Tr} \left[{\frac {\partial ^{2}S_{\operatorname {int} \Lambda }}{\partial \varphi \,\partial \varphi }}\cdot R_{\Lambda }^{-1}\right].$

(with ${\textstyle \partial }$ instead of ${\textstyle \delta }$)? Michael Hardy (talk) 04:42, 2 December 2024 (UTC)