Talk:Renormalization

message: This page should actually explain renormalization (as, say, in QED) rather than redirecting to "renormalization group".
Done! --Matt McIrvin 22:29, 9 Oct 2004 (UTC)

message: Need a little more clarification for laymen: is renormalization the only way to deal with infinity? Theoretically, if in the future human can tap in the unit of space - Planck length/Planck area/Planck volume - then all forces including can be measured down to literally each point in space? Is Planck volume significant? Can... Planck spacetime (to be the unit of spacetime rather than just space) be defined?Mastertek (talk) 14:32, 23 October 2011 (UTC)
thread_title: Speculative alternative to handle infinity

message: surely for the scientific american level crowd, a better intro can be provided, eg what the heck is a continuum ? etc etcCinnamon colbert (talk) 20:04, 15 September 2008 (UTC)
replies: text: Hi I had a try at a simpler introduction (I hope) -> User:Lcorman/Draft_Renormalization_Intro Could you give me some feedback on it ? Thanks ! Lcorman (talk)  —Preceding undated comment added 12:59, 17 April 2011 (UTC)
thread_title: incomprehensible intro

message: An anonymous user(86.130.62.19) added a link to an odd webpage. At a glance it appears to be just some understandably motivated bemoaning on the mathematically unrigorous nature of renormalization, propounding the virtue of fixing this problem. For the most part it is an excellent reference from POV skeptical of renormalization's valid(A POV which I share). Unfortunately, it happens to have a buried suggestion that Feynman, et al. were nothing more than frauds. Specifically I dispute its factual accuracy when it says about the award:
*1965. Feynman, Schwinger and Tomanoga, "for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles".I am not sure what the agricultural reference is about but all they were really proving was that if you subtract infinity from infinity, you can get any answer you want. Check out this recent paper by the Russian scientist V.P. Neznamov. By choosing a different renormalization method, he gets different answers for the Lamb shift and anomalous magnetic moment from Feynman, et al. He seems to be unhappy about this, but in my humble opinion, his unhappiness should not be with specific results, but rather with the fact that with some tweaking, he could get any other answer as well, including, if he really wants it, the "correct" ones.
This statement is very misleading to those who might read that page uncritically. I don't know how renormalization is done but I find this accusation highly improbable. However, this isn't the only guy making this charge of impropriety as a quick googling of "dippy process" reveals. Ideally, the article should talk about these accusations. I for one would like to understand how these people are confused on this matter. --Intangir 03:43, 31 December 2005 (UTC)
thread_title:  Dubious Weblink 

message: I have recently reviewed this article & found that it meets the criterion for being a good article. So I have promoted it to GA status. My congratulations to all the contributors for doing a fine job.
Cheers
Srikeit(talk ¦ ✉) 14:56, 27 May 2006 (UTC)
thread_title:  GA Promotion 

message: I heard that renormalization is used for computing the Feigenbaum logistic constants, a pure math topic, not physics. Should that go in the renormalization article? I was hoping to find an explanation here or at Feigenbaum constants. 75.62.7.22 04:03, 24 April 2007 (UTC)
thread_title:  renormalization in math? 

message: I am quite suspicious with the following reference : "A New Approach to Renormalization, Using Zeta regularization" (http://arxiv.org/abs/math/0402259). It has been withdrawn by arXiv administrators because of fraudulently claimed institutional affiliation and status. And to my opinion the preprint is quite poor and irrelevant, compared to other references. 
Therefore I suppressed it. 
Damien
Let me add that many links given in reference are no longer available (e.g. papers by Rivasseau and Zinn-Justin).
: The only "New Approach to Renormalization" that makes any sense to me is to stop doing it altogether. But even if one accepts it, Zeta function regularization is hardly a canonical approach and certainly not worth more than a footnote Cgoakley (talk) 08:26, 26 February 2008 (UTC)
replies: text: Now  has added an unformatted line: "Zeta regularization applied to divergent integrals}} General Science Journal ". It looks like a violation of Wikipedia:V#SELF, so I removed it. — Pt (T) 17:11, 30 April 2010 (UTC)
thread_title:  Problem with a reference 

message: In order to uphold the quality of Wikipedia:Good articles, all articles listed as Good articles are being reviewed against the GA criteria as part of the GA project quality task force. While all the hard work that has gone into this article is appreciated, unfortunately, as of February 25, 2008, this article fails to satisfy the criteria, as detailed below. For that reason, the article has been delisted from WP:GA. However, if improvements are made bringing the article up to standards, the article may be nominated at WP:GAN. If you feel this decision has been made in error, you may seek remediation at WP:GAR. 
GA review – see WP:WIAGA for criteria
#Is it reasonably well written?
#:A. Prose quality:  
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#:B. MoS compliance: 
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#Is it factually accurate and verifiable?
#:A. References to sources:  
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#:B. Citation of reliable sources where necessary:  
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#:C. No original research: 
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#Is it broad in its coverage?
#:A. Major aspects:  
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#:B. Focused: 
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#Is it neutral?
#:Fair representation without bias: 
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#Is it stable?
#: No edit wars, etc: 
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#Does it contain images to illustrate the topic?
#:A. Images are copyright tagged, and non-free images have fair use rationales:  
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#:B. Images are provided where possible and appropriate, with suitable captions: 
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#Overall: 
#:Pass or Fail: 
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--jwandersTalk 23:23, 25 February 2008 (UTC)
thread_title:  Delisted from GA 

message: Is the term quantum correction synonymous with renormalization?  70.247.169.197 (talk) 18:09, 14 August 2010 (UTC)
replies: text: This does not appear in the article so the context is missing. Guessing, I would say no. Quantum corrections to me means corrections from loops (in perturbation theory) or higher order corrections (in general) or off-shell particles correction (also general), which are all similar but not identical concepts. Setreset (talk) 11:23, 22 August 2010 (UTC)
thread_title: Quantum correction

message: The article does not focus enough on renormalization. It contains only 2 sentences on the process itself, under "Renormalization schemes". This is also reflected in the lead section which has a limited and unhelpful definition (assumes non-continuum regularization, besides not defining "continuum"). The latter I tried to improve. Setreset (talk) 11:22, 22 August 2010 (UTC)
replies: text: Also, it isn't sufficiently understandable and isn't readily understood by technical but non-specialist readers. A bit of attention in that area would help. It should be possible to ensure the concepts are better explained in overview without sacrificing technical rigor. FT2 (Talk | email) 02:34, 14 November 2012 (UTC)
thread_title: General comment

message: "A rigorous mathematical approach to renormalization theory is the so-called causal perturbation theory, where ultraviolet divergences are avoided from the start in calculations by performing well-defined mathematical operations only within the framework of distribution theory. The disadvantage of the method is the fact that the approach is quite technical and requires a high level of mathematical knowledge."
so basically "this (working) method has the disadvantage, that, to use it, you need to know math." odd statement. i don't know if this should be called a disadvantage. maybe one could say it is more "laborious" to use it or something like this. otherwise it could be said of any mathematical method used in physics that it has the "disadvantage that you need to know math" 92.196.116.53 (talk) 22:20, 19 September 2013 (UTC)
thread_title:  funny statement 

message: Supposing we have a theory that requires renormalization in order to give sensible results in diagrammatic approaches. Is that renormalization fundamental to the theory, or is it just an "artifact" of the calculation of perturbation expansion? Supposing I had an exact way of solving the theory, would renormalization still play a role? Nanite (talk) 01:20, 9 February 2014 (UTC)
replies: text: Yes, it is still necessary. Lattice simulations, for example, give a nonperturbative solution to quantum field theories, but many quantities (such as propagators) still diverge when taking the lattice spacing to zero. Furthermore, the connection between bare and physical parameters (such as masses) remains nontrivial, and renormalization has to be used to establish the relationship. MuDavid (talk) 03:56, 5 March 2015 (UTC)
thread_title:  is renormalization an issue only for perturbative methods? 

message: I keep seeing the terminology "protected" as applied to renormalization, but I'm not sure what it means.  Is this article an appropriate place to explain this terminology?  — Preceding unsigned comment added by 70.247.166.192 (talk) 03:28, 26 August 2015 (UTC)
replies: text: It means there exists something (usually a symmetry) making it unnecessary to renormalize the operator under consideration, i.e. the operator is protected from renormalization. I suppose it could be nice to note this somewhere in the article. MuDavid (talk) 08:28, 23 October 2015 (UTC)
thread_title:  "Protection" 

message: The greater the degree of renormalization, the more time that Feynmanian diagram version lasts. Of course all the infinite possible diagrams are extant, but simply for less time because unnecessarily complex diagrams (or particle pathways) are probabilistically less significant. Renormalization is actual though and bends measurably the paths of the particles at all scales. The graviton is simply a renormalization polariton (same concept).  — Preceding unsigned comment added by 2A02:587:4102:CF00:1963:F284:B24D:197C (talk) 06:24, 8 October 2016 (UTC)
thread_title:  Renormalization is physical, not theoretical, and causes [[gravity]], [[dark matter]] and [[dark energy]] 

message: There a several articles that link radiative correction to this article, yet there is no discussion of that term here?  I'm guessing there probably should be, and my feeling is that it would be beneficial to have a radiative correction redirect page as well, whether it points here or elsewhere. 75.139.254.117 (talk) 21:15, 14 March 2017 (UTC)
replies: text: I put in some plausible handles in this article. If you did a redirect page, send it to Feynman diagram, not here! Cuzkatzimhut (talk) 21:45, 14 March 2017 (UTC)
thread_title:  Radiative correction? 

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thread_title:  External links modified 

message: I can't think of any reason there should be an image of a penguin behind the penguin diagram. Showing that the penguin diagram looks kind of like a penguin is distracting to the rest of the article and pointless.  — Preceding unsigned comment added by 63.163.123.182 (talk) 19:35, 6 December 2018 (UTC)
replies: text: The Background penguin might answer an evident implicit question about the silly but established name... Cuzkatzimhut (talk) 17:13, 21 June 2020 (UTC)
thread_title:  Is the image of the penguin really necessary? 

message: Called by people who deem it a means to avoid causally important open questions.  — Preceding unsigned comment added by 2A02:587:410A:2A66:B176:F6E0:296B:D53E (talk) 16:18, 21 June 2020 (UTC)
replies: text: What's your point? Cuzkatzimhut (talk) 17:12, 21 June 2020 (UTC)
thread_title:  Procrusteanization 

message: Dear all, 
the article presently has a strong focus on renormalization in the context of high-energy physics.
However, the term renormalization is used in physics in a broader scope beyond high-energy physics and I think the introduction should reflect that.
There has also been a lot of debate on this talk page whether the introduction is accessible to technical but non-specialist readers. I think explaining the concept more broadly would potentially allow explaining some things more simply without having to delve into the complexities of the high-energy physics context.
Nevertheless, changing the introduction is such a way would clearly clash with the remainder of the article which almost exclusively focuses on the high-energy physics context. Therefore, I would like to first discuss the change here before doing an actual edit. I would be very happy about some feedback.
My proposal for an broader introduction that is hopefully more accessible is the following:
Renormalization refers to  a change of parameters of a physical theory that captures the effects that "microscopic" processes within the theory have on "macroscopic" processes. The distinction between "microscopic" and "macroscopic" processes is that the former occur on a smaller length scale than the latter. Given a parameter renormalization, the original theory can be turned into an effective theory for the macroscopic processes by discarding the microscopic processes from the original theory and and applying the parameter renormalization. 
As an example, consider a capacitor with a dielectric. Charges on the capacitor plates will polarize the dielectric. Consequently, the resulting electric field between the capacitor plates will be  weaker than the field that would be created by the charges alone. The parameter controlling the strength of the electric field created by charges is the vacuum permittivity. To describe the above effect, we have two options. We can work with a full microscopic theory that explicitly models the microscopic dipoles inside the dielectric or we can choose to only model the "macroscopic" charges on the capacitor plates. If we choose the second option, we have to renormalize the vacuum permittivity to account for the presence of the dielectric. The renormalization is the replacement of the vacuum permittivity by the dielectric's permittivity.
In the context of statistical mechanics and quantum field theory, effective theories and their renormalized parameters for macroscopic processes occuring on length scales that are larger than a so-called cut-off \Lambda can be formally derived. Calculating the evolution of the renormalized parameters as the cut-off \Lambda is continuously varied is the subject of the Renormalization group.
Renormalization was first developed in quantum electrodynamics (QED) to make sense of infinite integrals in perturbation theory. Initially viewed as a suspect provisional procedure even by some of its originators, renormalization eventually was embraced as an important and self-consistent actual mechanism of scale physics in several fields of physics and mathematics. Renormalization is distinct from regularization, another technique to control infinities by assuming the existence of new unknown physics at new scales.
Jascha Tempeler (talk) 07:33, 13 September 2021 (UTC)
replies: text: The "As an example ..." paragraph is clearly a pedagogical aside footnote, out of place in the introduction. What's wrong with a footnote? Remember, this article is not in the Wikiversity pages. Cuzkatzimhut (talk) 13:43, 13 September 2021 (UTC)
replies: text: Thanks for your remark @Cuzkatzimhut. In hindsight, I agree with your observation. Do you think it could alternatively fit into the body of the article under something like "Motivating example"? I hope that it allows people to get the overall idea in a simple setting. I thought I had seen similar things in other Wikipedia pages, but I understand your general concern about the article not belonging to Wikiversity. Jascha Tempeler (talk) 19:13, 13 September 2021 (UTC)
thread_title:  Working towards a more accessible introduction with less focus on high-energy physics 

message: This infuriating article suffers from a common Wikipedia malady: the author(s) assume the reader is already conversant with the topic. YOU JUST DONT DEFINE THE TERMS!  I sought this article because I wondered: “what is renormalization?”  No answer here.  The first paragraph tells me it’s used in science, blah blah.  BUT DOESNT SAY WHAT THE TERM IS!”  
Let me help the author(s):  start out:  “Renormalization is…” THEN DEFINE THE WORD!!  Geez!  Is that so hard to understand? 98.183.27.92 (talk) 01:40, 4 January 2024 (UTC)
replies: text: It took decades for physicists to understand what renormalization is but I don't think they treat it like that.  In mathematics, see chapter 7 of McMullen's book "Complex Dynamics and Renormalization".  What I'm clueless about is how the mathematical concept is related to the physical one.  An interesting place to start might be Feigenbaum's 1978 paper which is considered foundational.  I have not yet read this carefully but it looks approachable. 2601:644:8501:AAF0:0:0:0:2034 (talk) 19:55, 27 January 2024 (UTC)
replies: text: As emphasized in several items above, this article is not a tutorial in Wikiversity! It deals with one of the most technical and esoteric theories in physics, and of course it cannot define all terms. It is pitched to informed students and wannabe-experts, serving as a trail map. It does start by defining what Renormalization is (a collection of quantum field theoretical techniques) and segues to its modern essence, "Renormalization specifies relationships between parameters in the theory when parameters describing large distance scales differ from parameters describing small distance scales". It is the theory and techniques that achieve that. There is lots that is suboptimal in the introduction (I would demote the example in the second paragraph, for instance), but perhaps it is too much to expect a sharp idea of the subject; one might as well complain that the Category Theory article does not define  all of the  math terms involved! There are lots of popular science  videos on renormalization, but WP should not stoop to purveying bloviator stories to laymen. Cuzkatzimhut (talk) 22:10, 27 January 2024 (UTC)
replies: text: Seems like a non helpful answer, and it has always seemed to me that physics articles are worse than math articles at defining terms.  The category theory article doesn't define every term it uses, but it does say what a category is.  b:Haskell/Category theory is more accessible, though from a PLT perspective.  Also as someone mentioned above, the article is too much about physics.  I'd like to see some nonphysical examples, like the Mandelbrot set or the Feigenbaum constants.  I agree that a Wikiversity tutorial would be great.  2601:644:8501:AAF0:63BE:B01F:C826:5A26 (talk) 12:30, 28 January 2024 (UTC)
replies: text:  Of course the article is strictly about physics! If and when there are differently-focussed renormalization articles (all of them borrowing this term from physics, at a stretch), the title of this might have to morph to Renormalization (physics)...  The two sentences I adduced amount to a definition for the well-meaning reader.  I strongly believe it is superior to the old-fashioned and restrictive definition of the Britannica, "Renormalization, the procedure in quantum field theory by which divergent parts of a calculation, leading to nonsensical infinite results, are absorbed by redefinition into a few measurable quantities, so yielding finite answers".  I hope you appreciate this definition misses out on the more modern one in the extant third paragraph, quoted above!  Cuzkatzimhut (talk) 17:34, 28 January 2024 (UTC)
replies: text: Thanks, I'd be interested seeing some explanation how the math term is related.  In physics it sounds sort of like analytic continuation?  Like in QFT, you can solve an equation for an electron at point x, but if you attempt a perturbational expansion near x  the series diverges.  So you re-map the equation to push the singularity further away, recalculate, map again, etc.  Is it something like that?  I would say it seems esoteric because it arose from QFT which is itself esoteric, but renormalization per se should have a straightforward explanation inside somewhere. 2601:644:8501:AAF0:262A:2381:24CE:5477 (talk) 16:19, 29 January 2024 (UTC)
thread_title:  Definition