samedi 23 novembre 2013

Tais-toi et calcule (conjure le professeur de quantique à son étudiant) / échange et métacognitionne (propose le périphysicien à son lecteur)

Un rêve réalisé : une interaction constructive avec un blogueur du nouveau continent 
Pour célébrer mon centième billet sur ce blog, je me permets de retranscrire ici l'échange instructif que j'ai pu avoir avec le blogueur Matthew Strassler (qui est aussi et surtout professeur de physique théorique à l'université Rutgers et actuellement invité à l'université de Harvard) suite à son billet que j'ai par ailleurs déjà eu l'occasion de commenter ailleurs (mais pour d'autres motifs).

Thank you prof. Strassler for this synthetic and pedagogical defence of supersymmetry as a heuristic tool to improve : i) our understanding of the quantum field theories forged IN THE PAST and ii) build plethora of models for TOMORROW. But don’t you think that TODAY, at a time with only one Higgs boson and no superparticle detected by LHC so far (in agreement with null results of dark matter chasing experiments), it is time to focus instead on the possible conceptual reasons for the success of the only validated effective quantum field theory namely the Standard Model ? Now that (astro)physicists can reach so high energies and explore so huge amount of the unknown (but mostly empty!) universe don’t you think that priority should be put on mathematical and phenomenological consistency check of quantum theories ? Does supersymmetry ever help to deal with this topic ? My view is probably very naive but it seems to me that supersymmetry is not only a beautiful tool to enlarge the plato cave that fits with our prejudices (built on former empirical and mathematical experiences) but to say it crudely, it is also the most powerful tool physicists invented to sweep the dust under the carpet!
“it is time to focus instead on the possible conceptual reasons for the success of the only validated effective quantum field theory namely the Standard Model”
Yes, I agree with this statement, personally. This is what I’m doing. But it’s not easy… people have considered this for over 30 years and I don’t think there is a convincing story.
However, as I emphasized, studying supersymmetry has been extremely helpful in learning to understand quantum field theory in general. Several of my best ideas for dealing with non-supersymmetric field theories came from studying supersymmetric ones. I have just been reading up on the most powerful new tools for studying non-supersymmetric theories intwo spatial dimensions, many of which relied upon results and/or insights that emerged in supersymmetric contexts. So I think your statement “it is also the most powerful tool physicists invented to sweep the dust under the carpet!” really is too crude, not only in its tone but in its content. It’s much more elaborate and subtle than that. 
Thank you for the fast feedback. I don’t aim at being rude to SUSY, as you understand perfectly, the more so as it could show up “in our face” at any time from future experiments or from data currently processed by tenacious physicists.
On the theoretical side, nevertheless I have the feeling that supersymmetry has been oversold by the media and science outreach in general. I can understand that other mathematical tools, inspired by quantum physics, like quantum groups, Hopf algebra and non commutative geometry for instance are very hard to popularize but they seem to be less studied by theoretical physicists as well while they have proved to be useful : i) to .envision a mathematically coherent picture of renormalization, ii) to calculate the quantum numbers of the discovered Higgs boson and iii) to build possibly phenomenologicaly coherent SO(10) grand unified theory-like models (sorry for loosing non experts, I don’t intend to be pedantic, just specific).
Of course this is just a feeling from a “periphysicist” so to speak. I am not involved in research, just a curious educated hiker on the cybersphere looking for a piece of physics information to better enjoy the beauties of the world.
Once again Bravo ! for your work in this blog  
It is a fair point that supersymmetry has been somewhat over-studied (just because people like to play with it) compared to other promising ideas. This is partly because so much progress was made using it in the 1990s — that drew people in, of course. When there’s a breakthrough, people tend to go where the action is, but then they tend to stay longer than perhaps they should. It would definitely be good for people to spread out more.
//C'est moi qui ait naturellement mis en gras le texte ci-dessus car c'est son contenu qui motive la publication de ces commentaires dans ce blog-ci. Je trouve qu'ils font un pendant intéressant au billet précédent ...  

Philosophie (d'un blogueur du vieux continent) :
(Meta)Cogito ergo sum (periphysicus) 
je pense (méta) donc je suis (un périphysicien)

Pour prolonger un peu la métacognition (mot un peu lourd il faut en convenir) j'ajouterais volontier que le périphysicien (n')est (qu')une (modeste) tête chercheuse dans le monde virtuel, tandis que le physicien, comme chercheur accompli dans le monde réel, se doit d'avoir aussi des mains pour compter (manipuler les concepts et éprouver les hypothèses théoriques) et des jambes pour courir (à la chasse aux plus beaux phénomènes naturels et attraper les faits expérimentaux).

//ajout du 25/11/13
A propos de la première sentence du titre de ce billet (tais-toi et calcule ou shut-up and calculate) le  blogueur se doit de rendre à César ce qui appartient à César ou plutôt à David Mermin ce qui est parfois attribué à tord à Richard Feynman ... 

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Cher-ère lecteur-trice, le blogueur espère que ce billet vous a sinon interessé-e du moins interpellé-e donc, si le coeur vous en dit, osez partager avec les autres internautes comme moi vos commentaires éclairés !
Dear reader, the blogger hopes you have been interested by his post or have noticed something (ir)relevant, then if you are in the mood, do not hesitate to share with other internauts like me your enlightened opinion !