In one of my previous articles, I was discussing particles and quantum fields, and more in particular how to introduce those concepts to laymen (and thus Steemians) in a correct and simplified manner.
[image credits: CERN]
I move on here and tackle the concept of gauge symmetries.
I will in particular use timezones (something that everyone knows) to explain how this works.
In particle physics, this is crucial to describe how all fundamental interactions work at the level of the elementary particles (except gravity).
GAUGE SYMMETRIES
Let us start with the concept of a symmetry. A symmetry is a transformation of the mathematical objects of the theory that does not alter the physics, or in other words, the predictions.
[image credits: Wikipedia]
Now, let us move on with gauge symmetries and an explicit example. Let us imagine we carry a physics experiment somewhere on Earth.
Obviously, the timezone corresponding to the place where the experiment happens does not influence the results.
That is exactly a symmetry: we are allowed to use different timezones in different places and the physics is invariant of that.
We now need something that tells us how to the timezone changes from point of space to point of space and to relate the different possible choices. Obviously, this must be some vectorial object (with a direction in tridimensional space).
Generalizing this to the quantum field theory level, the vectorial object becomes a field, and thus a new particle: the so-called force carrier.
Things are actually slightly more complicated, but I hope you got the main concepts here: interactions are connected to force carriers.
INTERACTIONS IN THE MICROSCOPIC WORLD
We should first forget gravity. The reason is very simple.
The gravitational interactions involve the masses of the particles that interact. However, the masses of the elementary particles are small, so that the resulting gravitational strength is tiny and negligible. This even holds for the heaviest of all known particles, the top quark.
Of course, when one says negligible, it is always negligible relatively to something else. Here, the something else consists of the strengths of the other interactions.
Consequently, the Standard Model of particle physics is the theory that describes how the elementary particles propagate in space-time and interact, and by ‘interactions’, we mean electromagnetic, weak and strong interactions only.
ELECTROMAGNETISM
[image credits: Pixabay]
Electromagnetic interactions involve electric charges, and their strength is actually proportional to these charges.
At the macroscopic level, matter is generally neutral, and thus electromagnetically blind.
Matter is indeed generally comprised of an equal number of positively-charged and negatively-charged constituents.
All electromagnetic effects that would be induced by the positive charges constituting matter are thus compensated by those of the negative charges.
At the microscopic level, the situation is very different. Elementary particles are mostly not neutral, and electromagnetism consequently plays a role. It explains, for instance, how atomic nuclei and electrons form atoms.
Equivalently, electromagnetism is crucial to explain the structure of matter.
THE WEAK AND STRONG FORCES
[image credits: Pixabay]
The weak and strong forces have been discovered in the contest of radioactivity, and they are purely related to the microscopic world.
There is no macroscopic effect at all (those forces are actually short-ranged).
The strong interaction is responsible for the cohesion of the protons and neutrons. Neutrons and protons are composite objects made of elementary quarks and gluons that are glued together by virtue of the strong interaction.
At the atomic level, neutrons and protons form atomic nuclei, once again by virtue of the strong interaction.
As a consequence, the strong interaction is one of the main building blocks to explain the structure of matter, as for electromagnetism. The weak force, much weaker, has in contrast not any effect on the structure of matter.
It instead renders decay processes possible, and these processes are slow as a consequence of the weakness of the weak force. This slowness for instance allows our sun to burn its fuel at a moderate pace.
SYMMETRIES AND INTERACTIONS
Starting from a symmetry concept, gauge theories explain how the interactions of the elementary particles are modeled by the exchange of force carriers, namely the photon (electromagnetism), the W and Z bosons (weak interaction) and the gluons (strong interaction).
[image credits: homemade]
This exchange of a force carrier is illustrated on the picture on the right. The ball stands for a gauge boson (which is the fancy word used for a force carrier).
The two little guys are two particles and the ball is passed from one to the other. As a result, the two boats will move away from each other. One says that they interact.
A good question is why we are so sure that this picture involving gauge symmetries is the correct way to describe the microscopic world? We can never be sure, and a theory has to be tested. Data then tells us.
The predictions of the Standard Model have been intensively confronted to data during the last 50 years. We are talking of several thousands of different measurements. There is (almost) not a single sign of any deviation up to now.
Relying on gauge symmetries seems thus suitable to explain all particle physics data available today. More importantly, predictions are made for future experiments so that further tests will be carried on.
SUMMARY AND REFERENCES
In this post, I have discussed the notion of gauge symmetries and how it is related to the fundamental interactions.
I have first defined what is a gauge symmetry and show how this is related to the so-called force carriers. Then, I have focused on the fundamental interactions that are actually described by gauge symmetries.
The topic discussed in this article has been inspired by my reading of this paper that addresses the teaching of particle physics. The last part of the post is made of well-known stuff that can be found everywhere (just wikipedia it for instance or check my old blog).
Particle physics is a higher course in university and in graduate courses.
So they are beyond steemit syllabus, i believe.
Even if Steemit had a syllabus (which it doesn't) and this article was beyond it (which it isn't). How can Steemit grow if we don't we don't push the boundaries of the usual Steemit fare to attract new readers and potential members?
As a newcomer here, I was delighted to find someone making contributions of such substance and will be following @lemouth.
Thanks for your very kind message :)
I do not see it from your perpectiva @mohammedfelahi, the classes of quantum mechanics and I present them during my undergraduate studies, ie I saw 2 subjects related to the physics of the particles and I think they are very important to understand in a microscopic way the behavior of the universe . If you do not have a base of quantum mechanics as you could do a postgraduate in this specialty? it would be very complicated to agree ?, then it is essential to have notion about it, in my university in Venezuela specifically the University of Zulia there are excellent teachers in charge of teaching these classes, with much experience and studies in recognized universities worldwide. eye I am not an expert in particle physics but if I have the basic knowledge.
I disagree. I already discussed particle physics with high-school kids. And the message passed pretty well. Everything depends on how things are explained.
Great work as always @lemouth. Electromagnetic forces are like picking up coins with a magnet eh?
"Please upfollow, thank you. Vote follow up please thanks. Up up"
Just wanted to make you feel comfortable and give you a more normal comment. ;)
I actually looked for a magnet picture on pixabay, and this one appeared. I couldn't resist using it :D
Really nice explanation of gauge symmetries. Although you mentioned this in in laymen terms, and I was able to read and understand it (have beta uni background) I think for many it is still quite difficult! :) but that is beside the point :) I learned something today at least.
It is always more difficult when writing than when speaking in front of an audience. I can imagine some people, without any university-level background, can find this difficult. I would be more than happy to continue the discussion in the comments :D
Thanks for passing by, by the way :)
I would really love to learn more about particle physics. Can you give me an outline of references and on what to read first? Coz if I jumped directly here, I wouldn't effectively understand this. Thank you Sir @lemouth...
It depends on your background. I need to know what you currently know and whats you are looking at (university-level textbooks, popuilarization books, etc...). You can also check some of my posts for basic introductions :)
Sorry for the late response Sir, throughout my academic years I only learned basic physics such as projectiles, speed & velocity, vectors, forces etc. no complicated physics like the theory of relativity and others. My knowledge about those things is just small and I find it hard to explain when I do not fully understand the topic.
If you know what are vectors and forces, there are ways to start. I myself wrote a book on quantum mechanics where the only requirements are integration, differentiation, vectors. However, it is not in English, and I don't know any English equivalent.
All the good books I could recommend are actually more advanced. You can possibly try the Cohen-Tannoudji but I am afraid it may be a bit too advanced. This is considered as the bible for quantum mechanics.
It's okay Sir, thanks for the advice by the way.. Anyways I am watching minute-physics in youtube and I learned a lot there, would you recommend it?
I am not watching online videos (I am a reader guy), so that I am afraid I cannot speak for or against them. Sorry :)
good post, please upvote me
Would a -100% upvote be OK? :D
stop being mean to me :(
I’m trying to get my head around particle physics. Though it’s quite complex for the uninitiated, but with posts like this, understanding of it will be enhanced. Thanks for sharing
My pleasure to share! :)
Super article, n'étant pas le meilleur en anglais quelques éléments m'échappent mais en tout cas beau travail ! J'adore la physique mais je m'y connaît moins que toi. Sinon feras tu ce post en français ?
Je le traduirai avec plaisir... mais @ixindamix a fait une commande avant toi ;) Donc il faudra patienter (en general, je fais une traduction par semaine).
Thank you for the in -depth explanation @lemouth , learned quite a bit about gauge symmetries!
You are very welcome :)
Cool
Thanks for sharing this!
It would be a good experience for your happy life
Thank you for your posting
Wow,, great of science,,
Thanks for information @lemouth
https://steemit.com/@indramaulana
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