In the so-called anarchic scenarios the hierarchies of SM fermion masses are generated through the hierarchies of mixings and anarchic composite sector couplings. The light fermions are almost elementary while the third generation is strongly or entirely composite.
This leads to a structural suppression of all effects that involve first two generations that are the most precisely measured. In particular flavor transitions and corrections to electro-weak observables are suppressed. Other scenarios are also possible  with different phenomenology. Supersymmetric models also predict that every Standard Model particle will have a heavier partner. However, in supersymmetry the partners have a different spin : they are bosons if the SM particle is a fermion, and vice versa.
In composite Higgs models the partners have the same spin as the SM particles. The mixing of the SM particles determines the coupling with the known particles of the SM. The detailed phenomenology depends strongly on the flavor assumptions and is in general model-dependent. The Higgs and the top quark typically have the largest coupling to the new particles. For this reason third generation partners are the most easy to produce and top physics has the largest deviations from the SM. Top partners have also special importance given their role in the naturalness of the theory.
After the first run of the LHC direct experimental searches exclude third generation fermionic resonances up to GeV. Deviations from the SM couplings is proportional to the degree of compositeness of the particles.
Naturalness in low-scale SUSY models and “non-linear” MSSM
For this reason the largest departures from the SM predictions are expected for the third generation quarks and Higgs couplings. The first have been measured with per mille precision by the LEP experiment. The hypothesis of partial compositeness allows to suppress flavor violation beyond the SM that is severely constrained experimentally.
Nevertheless, within anarchic scenarios sizable deviations from the SM predictions exist in several observables. Overall flavor physics suggests the strongest indirect bounds on anarchic scenarios. This tension can be avoided with different flavor assumptions. From Wikipedia, the free encyclopedia. Dugan, H. Georgi and D. B, Agashe, R. Contino and A. Pomarol, The Minimal composite Higgs model , Nucl. Mrazek, A. Pomarol, R. Rattazzi, M. Date de parution :. Sujet :. ISBN :. No de produit :. Format :. Adobe DRM.
Suivi de commande. Mon compte. Concluding that at least one of these is the case — which will take a long time — would be a very big deal, conceptually. It would change the questions that scientists ask, and could mark a major shift in the history of the field — much like the Michelson-Morley experiment was a watershed event not so widely recognized, though, at the time whose impact on our understanding of nature was immeasurable.
So a small average Higgs field value implies small Higgs boson mass, and a huge average Higgs field value implies huge Higgs boson mass, which is why of course the LHC thought it might find the Higgs. Conclusion : there are no solutions to naturalness assumed problem as in fact there is no problem in my subjective view. I mean by subjective your decision that such and such properties are not expected biased by you priori decision that ANY kind of universe is possible which no theory can prove. Now hear this: what about the QF fluctuations that are extremely tuned to result in the UP?
You would say it is extremely un-natural. But what if there exist a selection force that renders that relation very very natural? Our physics cannot tell…… Physics beyond physics may tell. Matt, about Fig. For electric field, you can measure the force on a charge placed in the electric field and calculate the value of the electric field at the point. The second part of this article is very interesting and helped me understand some important details.
That would be the last thing I want. For example; it withstands such a physical abuse from supernovae explosions, constant radiation of the worst kind, torquing by the gravity and the mad speeds and spin of celestial objects. Could you please write something about the vacuum. I know that quantum fluctuations are happening on a quantum scale, not in an everyday cup of space that we can see and observe.
The virtual particles are said to be popping in and out of existence so much that this phenomenon is viewed as a constant of a vacuum cosmological constant. I deduct from what little I know, that vacuum is a medium, just like air or water are here on earth, that can absorb things, store the radiation and make it a part of itself. When physicists observe the virtual particles, they must do that test in some depressurised cylinder. Could that be the reason for the appearance of the virtual particles, Depressurized vacuum is actually experiencing the pressure created by the walls of the cylinder.
Is there any evidence that vacuum in space also produces these virtual particles? Has this been proven? Hope you can answer this one, professor. Other fields have other definitions e. Eg Unruh radiation for accelerated objects; Hawking radiation around black holes; static and dynamic Casimir effect. Your physics speculations in the rest of the comment are not contacting any of what we observe and know about the actual physics. Most of it fits, I hear with exception to cosmological constant.
What is the principle here, that energies of the universe have to balance out? All the positive energy of the fermions which are just another state of energy has to cancel out all the negative energy of the universe, which is the energy of the forces their fields and bosons. This universe is on the go. If fermions are energies in another state then everything there is is energy. There is no need to balance anything out. The problem is not in unnaturalness of nature but in unnaturalness of an approach.
First solve the problem of gravity. Is gravity truly the fourth force or is it an effect caused by other factors. In that case universe will have only three forces operating upon it. The ratio could be as low as one to two. Due to all the cancellations that different forces have on each other. In your theory though, nature is precise. Nature has imposed some strange effect on me without me even know it. Same principle applies to the universe, I should think. So, the problem of naturalness is man-made.
If you think about it, what other phenomenon it could be? Funniest part comes when you derive a model based on spinning, everything comes crystal clear. It mentions perfect vacuum and partial vacuum. Regardless of that, vacuum suppose to have fluctuation of energy that can be measured and observed. We have to start to visualize another picture of how universe started, the possibility that mater popped out out of the vacuum itself and that vacuum existed before the matter.
The current quantum fluctuations could be the end state of the vacuum that could have been a lot denser before. You say; BB created space vacuum. CMBR means nothing of the sort. You are looking at magnetosphere of either this galaxy, cluster of galaxies or universe itself but how can you know for sure which one. The weak radio energies prove nothing unusual, least that BB occurred.
Tell me if universe has a magnetosphere or that there is no difference between the space of our universe and hyperspace or whatever you wish to call it, if multiverse is reality. If BB never happened, then it changes the picture of what reality is. Unless anyone of you physicist is willing to forget for the moment all you have learned and accepted to be the truth of reality and take a fresh new approach to this universe and nature of it, you may never solve this problem of seaming, emphasis on seaming unnaturalness of our universe.
If you get lost in the detail of the picture, you may miss the whole meaning of it. Too close to the trees to see the forest? Oh, and when you make an appeal to frequencies of events die throws , you would here make an appeal to multiverses. Well, Matt was considering a fair dice, he could calculate rough probabilities within our universe. Lots of. Excellent explanation as usual, Professor Strassler. You really do have a gift for coming up with apt analogies.
In the spirit of helping you polish this article, I have noted some typos in the most recent addition. I also have an observation — throughout the most recent section, you claim that if vmax is near GeV, there is no problem, and that we do not know what vmax is. This most recent section of your article does a good job of convincing me that the naturalness problem increases as vmax increases above GeV, but you have provided no evidence that vmax is indeed greater than GeV.
Is there some reason we have to think that vmax is so big that there really is a problem?
The obvious solution is indeed that vmax is near GeV. And if that is true, the LHC will discover as-yet unknown particles, and other predictions of the Standard Model will fail as well. The strongest evidence against it — inconclusive at this time — is that the LHC has not yet discovered any such non-Standard-Model particles, and there are no known deviations from the Standard Model at the current time.
Arguably we should have seen subtle deviations already by now. But I will get to this issue soon. This is exactly similar to my comment on the explained post , I guess there are some confusion here. Therefore each yet to be known particle is an indication of a field that somehow interacts with other known and unknown fields?
Would a black hole singularity be in essence, matter broken down to its constituent fields and tied up, or not, or compressed into a knot? As to a Creator or not, I have had my own personal experience, however it is best not to argue over something that cannot be accepted by many for their own personal reasons. This should not be a blog about Religion. There is such a thing as vacuum — the universe is much emptier than you think. So the universe has lots of vacuum, on these distance scales.
The old grandmother of 15th century comes back to see her grand … grandson, the Apple boy. The following is the conversation about this unnaturalness issue. Apple boy: G-grandmother, I just read a great article about the unnaturalness of Nature. Every argument in it makes sense. How can Nature be unnatural?
You have sat right beside Nature for the past years. Can you help me on this? G-grandmother: Oh, the only thing unnatural to me during my last visit in the 17th century was seeing a man who walked on a rope feet above the ground. Apple boy: It is unnatural to an average person in their ability to perform such a stunt. But, it is simply allowed by the laws of Nature.
G-grandmother: Well, I really see some unnatural things in this visit. When I came down from upstairs, I saw many people in a bird-like metal box flying in the sky. Then, I saw many people talking from a hand-held plate. Apple boy: Indeed, they are some kinds of unnatural as they were invented by humans.
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We call them artificial inventions. Yet, they are still parts of Nature as only laws of nature allow their existences. G-grandmother: Last night, I saw a video about Ptolemy model of the universe, and all stars are dancing in different patterns. How can a star dance like a dancer? It is truly unnatural. G-grandmother: Why is it unnatural? For a few hundred years, I have travelled with my nephew Jedi all over this universe. And, most of the time His saying is true only when my spaceship landed on Earth. There must be some unnatural force around Earth. Apple boy: Okay, okay.
No analogy. But, please read the entire article. The argument is very strong individually, especially about the Standard Model. G-grandmother: Hi, boy, it took me awhile to read it. No big problem, but a major confusion. There are only two questions. Standard Model is unnatural meaning, it is wrong. Nature is unnatural meaning, … nuts. Apple boy: The issue is more subtle than that.
The Standard Model has three parts. Part A — A zoo of particles especially the 48 matter particles which are verified by tests. Part C — A reverse-engineering which produced Higgs mechanism. If Standard Model is wrong unnatural , which part is wrong? G-grandmother: Part A is message directly from Nature. Part B is artificial but works for Nature. Only part C is the suspect of the problem. This is an unsettled issue and thus no need to go into any further.
If a set of laws can be tuned, it becomes many different sets. If we change the nature constants very slightly, this universe will be dramatically different. G-grandmother: Well, this is another major confusion. Preciseness looks very much like fine-tuning but cannot be tuned. Apple boy: Thanks G-grandmother. Now I understand the issue which has only two questions. Which one is unnatural —- Nature or the Standard Model 2.
Can preciseness be tuned?
Higgs Potential and Naturalness After the Higgs Discovery
Quantum fluctuations of quantum fields, and the energy carried in those fluctuations the vacuum energy 3. G-grandmother: I was a farm lady, you know. Apple boy: Come on, G-grandmother. A herd of sheep, a pack of dogs and a school of fish, not fields. G-grandmother: Okay, my bad. Just exclude those then. But, for all other fields corn or the whatnot , I could turn them on or off as I please, by plowing them out or seeding them in.
G-grandmother: Just a bit Buddhism here. All those fields are transient phenomena. Their on or off have no importance for the eternal reality. So, those summation operations of all those different fields top quark field, etc. By the way, if a field can be turned on or off, it cannot be the true Daddy field. G-grandmother: Now, you ask a right question. It is the space-time sheet field. All matter particles are protrusions from the space-time field. When an electron protrudes, it forms an electric field. Apple Boy: So, Higgs field is not space-time field.
Is there anything wrong with the Higgs field argument in this unnaturalness issue? G-grandmother: This is the whole problem. The argument implies that the Higgs field is the true Daddy field which affects the entire universe. Any other fields also carry energy, but not vacuum energy. Apple Boy: Come on, everyone knows that the vacuum energy is the result of quantum fluctuations of quantum fields. G-grandmother: No, the quantum fluctuations of electric field are not vacuum energy. This is a linguistic issue, you know.
So, vacuum energy is about the energy carried by space-field space-time-sheet to be exact. Apple Boy: Well, besides of not being turned on or off, what is the other reason that the Higgs field cannot be the space-time-sheet? If Higgs field does not house all fields, its being on or off does not truly make any difference to the space-time-sheet. If it does house all fields, then it cannot be turned on or off. All those calculations are just games on the paper. G-grandmother: Wow, you got a key question again. We know three facts. Quantum principle fluctuations is a fact.
Vacuum energy is not zero. The above two facts a and b are related. There are two possibilities. Quantum principle fundamental causes the nonzero vacuum energy emergent. Nonzero vacuum energy fundamental causes the quantum principle emergent. By selecting 1 as the answer, we are facing the unnaturalness issue. By selecting 2 as the answer, the Nature cannot be unnatural.
But, this issue is very deep and cannot be discussed any further here. This is fantastic — the way you explain things makes the investment of a little work on the part of the reader very rewarding, as I am now feeling quite close to really grokking the whole thing, after years of reading explanations for non-specialists that skirted around the tricky parts of the logical argument, leaving the reader unsatisfied even after effort. Physically, this is the scale of energy above which precise calculations of scattering experiments require inclusion of gravity effects… where gravitational forces are just as strong as the other forces.
Have I answered you? Thanks for your answer. These are the blue curves in Figure 5. Whether or not there are any red contributions, the sum of blue and red contributions must correspond to what we observe. And what we observe is that the Higgs field has an average value of GeV, and the energy density of empty space is such-and-such. Now, the blue effects are in principle—and, to a large extent in practice—calculable, you say.
The absence of any new particle physics would mean that the limiting value for the Higgs energy occurs when the top quark gets too heavy for the rest of the Standard Model to work. This is really really really big, and so the absence of any new particle physics at higher energies means the coincidence of cancellation, with such a wide range of potential universes to choose from, is that much more startling. You have the logic up-side down. Not quite.
What it would certainly do is make it more obvious why GeV would emerge from our equations, instead of zero or something much larger. Let me explain some of the solutions; then it will become clearer what I mean. Fields have both value how big is the field at this point and energy how much energy is associated with the field being this big. Only if you make an enormously different choice can you make the problem evaporate.
But successfully justifying that choice would represent, in fact, an example of creating a new solution to the naturalness problem. There are only a few such solutions that have been proposed over the past 35 years. But by range, I meant the range of hypothetical universes that we are imagining ours being chosen from, not only the range of values of the Higgs field. But this seems on the face of it, to one particular layperson at least i. Clearly the precise numerical likelihood that you compute depends on what possibilities you consider, and we have no idea what options nature had available, if any.
This is a way of arguing that the Standard Model and its Higgs field are not likely to be the whole story for particle collisions with energy well above GeV. Universe appears to be unnatural or, opposite to what was expected and suggested by A. Could this be because universe is open system and not closed, as almost everyone thinks of it. Say it was a deliberate act, planned, etc. In the blue,red and green curves, I suppose you are assuming that there is only one Higgs field and one Higgs particle at the currently known values.
Does having more Higgses at higher and higher energies help with the fine tuning problem or make it worse? In other words are more Higges buried in high value of v max? The argument would be entirely unchanged; adding more Higgs fields does not give any natural cancellations, and the problem would now be just as bad. Is the un-naturalness problem totally dependent on our assumption that the primary cosmic fundamentals are Fields so that if in the year it was proved wrong assumption then the U-N problem vanish , or it is itself some kind of fundamental rank problem , in other words , are ANY fundamental building blocks tied to un-naturalness?
However, if fields were replaced with something else in the GeV range, we would have expected predictions from quantum field theory for physics at the Large Hadron Collider to begin to fail at the highest energies. Instead, those predictions work very well. I mean : maybe the un-natural is the field concept despite the correlations between the data and the assumption.
The spectacular cancellation between known and unknown large quantities is what is unnatural. It is not concepts that are unnatural here. The known large quantities will still be there… because we know quantum fluctuations of known fields exist and have large energy. You are really a true scientist , honest , sincere and wonderful person Matt. All respects and regards are due to you for your most respectful science. It seems logical that changing the Higgs field value increases the energy of empty space and that makes it more difficult to vibrate the field.
For the other particles the mechanism of getting mass is through interaction with the Higgs field. Not because changing the electron field value would increase the energy of empty space. Is that correct? Because my understanding is that if the Higgs field were zero, the other particles would be massless — so the zero point energy would not help them get their mass. Or the zero point energy would give them some very small mass even without the Higgs field? Very good question. I have to think about whether I can improve this.
For all fields that we know so far and this may not be true of other fields currently unknown , the mass of the particle is associated with the Higgs field in some way. However, the story for the Higgs particle is slightly different from the others. About the Particles: This is the same, in a sense, for the Higgs and for everything else. It is true that particles like the electron get their mass by interacting with the Higgs field. But how does that work in detail? An electron is a ripple in the electron field. That means that the electron field, which is normally zero in empty space, is non-zero as the electron goes by.
This is general. The issue is: by how much does turning on a field like the electron field increase the energy of empty space? The amount by which it increases tells you something about the mass-energy of a ripple in that field. In particular that there are quark and gluon condensates characterizing the vacuum. Good point. Quark and gluon fields do not have any such issue, but composite fields made from a combination of quark and anti-quark fields, and from pairs of gluon fields, have this issue.
You state Vmax is how far you could push the value of higgs field within the tolerance of the standard model, but that does not seem to imply the real field has to be high, in fact unless I misunderstand it is deemed to be which is low and does not need any unnatural factors — so why do you need to push the foundations of the model that far? The point here is not to put the cart before the horse. Yes — but even according to your text does not have to be the absolute but just the regional minimum so why strain a good model to breaking point?
Not sure I understand you yet. We want to understand whether the good model could be the complete model or not. If it is the complete model, then the thought experiment of pushing up the Higgs field to large values should be legitimate. Which leads us to think it can only a good model up to around GeV, and then we should expect other phenomena to start showing up, or maybe something else weird is going on.
Sorry seems Im the one who does not understand but not sure where I go wrong: There is one higgsfield at GeV — correct? Because its there, there has to be minimum in the energy density at this level —? We dont know why but we dont need any unnatural factors to make it so? Say it this way: Suppose you know a car can go at mph, but you discover the car is going at 60 mph. Now you want to explain: why is at 60 mph, given that it can go mph? One way to find out is: try running the car maybe just in your mind at mph, at mph, at mph, at 20 mph, at 30 mph. But now imagine, for example, that you had a car that could go mph, and had an engine that was powerful enough to go that fast in the absence of friction.
Our problem is vaguely akin to this. Thanks for your questions. You and several other commenters are finding a number of pedagogical flaws. Not class 3. Going through the comments I think I was asking the same as JonW in a somewhat naiver way and thanks to your explanations to me and also to him I think I now finally get the picture more or less. You could imagine that, but now make equations that actually do it. Then, having succeeded, make a prediction based on those equations.
That, too, may be difficult. The maths to do that is beyond me, but I would predict that a mixture of opposing universes would not be very stable, at least not for a sufficiently long time to get to the present stage. At some time matter must have sprung from fields at some point in the creation of the universe?
Of course that would be the particles that later became Hydrogen and Helium, etc.. You can speak of virtual particles which spring in and out of existence evidently due to the peaks in waves that fields have, I would think. Please excuse my less than knowledgeable questions. Strassler The fact that things are cancelling out and the total energy is nearly flat is another way of saying that there is some unknown symmetry in nature! And what is that symmetry if it is not supersymmetry. I would like draw you attention to a recent blog by Sean Carrol where he discusses the early results from dark matter searches which are giving hints of dark matter at GeV energy levels.
He pointed out that if that turns out correct, then there might be roughly equal number of baryons and dark matter particles which might have something to do with baryon number conservation. What kind of symmetry can give rise to equal number of heavier but not that heavy dark matter candidates.
And other results point to interacting Exciting dark matter pointing to presence of dark electromagnetism like forces that do not interact with electric charge. A symmetry is only one possible explanation. Dynamical effects can cause this also. I will discuss this soon.
Regarding dark matter: again, a symmetry is only one possible explanation.