User talk:Bakken

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Your recent edits
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What's up
So you don't like the Higgs mechanism page. But I don't understand what you don't like, and you keep on putting in a standard-model specific version which is not satisfactory. Will you tell me what points you dislike in the current lead?Likebox (talk) 18:51, 9 November 2008 (UTC)


 * can you tell me what you dislike in the first sentence of the last edit of MichaelCPrice?


 * I don't like standard model specific stuff. The Higgs mechanism is when there's a vacuum condensate and a gauge boson gets a mass. In the standard model, the Higgs is a sector and it does electroweak symmetry breaking. These two ideas should not be mixed up.Likebox (talk) 19:03, 9 November 2008 (UTC)


 * In addition, there are factual inaccuracies. "All fields" do not acquire mass by interaction with the Higgs, only those fields which can get a mass by a renormalizable interaction with the Higgs (and the gauge bosons). For example, the neutrino does not get a mass from interaction with the Higgs in any renormalizable way. If you added a chiral fermion with a big hypercharge, and no partner, it would stay massless too after higgsing.Likebox (talk) 19:06, 9 November 2008 (UTC)


 * "In particle physics, the Higgs mechanism is a proposed framework where the otherwise massless particles acquire effective masses via their interaction with a background Higgs field." -- what is model specific here?


 * That one sentence is not model specific so much as it is imprecise. The Higgs mechanism is when charged condensate makes gauge bosons massive. It will not necesarily give mass to spin-1/2 particles, that's a completely separate effect. In addition, in certain models, interaction with the Higgs will give new cubic and quartic terms in the Lagrangian, new interactions, not new masses. I am getting tired of arguing, because I get the feeling that you don't really understand the Higgs mechanism at all, but that your only goal is to copy the language from mediocre textbooks into wikipedia.Likebox (talk) 19:23, 9 November 2008 (UTC)


 * "In particle physics, the Higgs mechanism is a proposed framework where the massless gauge bosons acquire effective masses via their interaction with a background Higgs field." Do you think this is more precise? You try to distinguish the Higgs effect for making the gauge bosons massive from the effective masses of fermions. I could agree with that, but unfortunately, the Particle Data Group apparently uses the concept "Higgs effect" for both. Now, why should your opinion have a priority over PDG? Bakken (talk) 19:33, 9 November 2008 (UTC)


 * Because PDG is not interested in communicating the notion clearly. They are interested in making a catalog of experimental data on particles. If we were arguing about the width of the rho meson, the PDG would be a reliable authority. On issues of how to explain theory, they are not the best source.Likebox (talk) 19:36, 9 November 2008 (UTC)


 * "In particle physics, the Higgs mechanism is a proposed framework within a gauge theory where the massless gauge bosons acquire effective masses via their interaction with a background Higgs field." Is this better?


 * Yeah--- that's perfect. But that's what I keep writing and you keep erasing.Likebox (talk) 19:59, 9 November 2008 (UTC)


 * Oops... sorry. I didn't see the change from before.Likebox (talk) 20:02, 9 November 2008 (UTC)

Condensate
I'm assuming that by "condensate" everybody means an Einstein-Bose condensate? --Michael C. Price talk 11:07, 27 April 2009 (UTC)


 * Well, I guess it is more a vacuum expectation value of a field which, if non-zero, is called a condensate. Bose-Einstein condensate (BEC) is a quantum system of non-interacting bosons in the ground state of an external well. The Higgs condensate is more like a strong classical field a small excitations from which are the quantum particles -- Higgs bosons. So, in my opinion -- no, Higgs condensate is not a BEC but rather a non-zero expectation value in the ground state (vacuum) of the theory.--Bakken (talk) 11:30, 27 April 2009 (UTC)


 * I see that a site that Kibble maintains says "The mechanism is essentially a relativistic version of one that operates in a superconductor.", which implies we are dealing with superfluity and hence some form of a Bose-Einstein condensate.--Michael C. Price talk 11:22, 29 April 2009 (UTC)


 * Well, than you have to tell me what are those non-interacting bosons that make the alleged BEC in our case. What are they? Certainly not the Higgs bosons themselves, since we don't see them around at all. What then?


 * The question is, can a BEC be composed of self-interacting bosons? It would seem it can be, according to people (such as Kibble) who know more about these things than me.  Doesn't sound that unreasonable, provided the interaction with other particles is much less than their self-interaction and mass couplings.  Being a superfluid renders them invisible, of course. --Michael C. Price talk 12:43, 29 April 2009 (UTC)


 * "The question is, can a BEC be composed of self-interacting bosons?" -- only if the interaction is very weak and does not change significantly the spectrum of the system. But it is even simpler than that: there are no particles in Higgs condensate at all! Because quantum particles are exceedingly small excitations of the field from its ground state. The Higgs bosons are exceedingly small excitations of the Higgs field from the Higgs condensate. The Higgs condensate is *not* a BEC made of Higgs bosons, because the Higgs bosons themselves are exceedingly small excitations of the Higgs field from the Higgs condensate.--Bakken (talk) 13:54, 29 April 2009 (UTC)


 * Superfluid is a very complicated many-body systems of strongly interacting particles with a very peculiar low-energy spectrum. Higgs condensate is *not* a superfluid -- it's simply a number. It is not made of particles at all. It is a constant field filling up whole space.--Bakken (talk) 13:54, 29 April 2009 (UTC)
 * It certainly is a field filling the whole of space, but is it also a superfluid? One model does not exclude the other.  (Low-energy is a relative term, of course.  Today's temperatures are low compared with the Higgs symmetry breaking temperature.)   If the Higgs condensate isn't a superfluid then why do Kibble and others talk about superconductivity so much?  Superconductivity always requires a superfluid. --Michael C. Price talk 16:11, 29 April 2009 (UTC)


 * I guess that's because they have this analogy with Meissner effect.--Bakken (talk) 17:08, 29 April 2009 (UTC)


 * "but is it also a superfluid?" -- simply ask yourself what a superfluid is and then compare your definition with the Higgs condensate which is a constant field throughout the space. Than you will yourself answer that question.--Bakken (talk) 17:08, 29 April 2009 (UTC)
 * The Higgs condensate having a definite field value is compatible with the BEC condensate / superfluid having an indefinite particle count. --Michael C. Price talk 21:01, 29 April 2009 (UTC)
 * In my view BEC and superfluid are two completely different and largely unrelated phenomena. BEC is a dilute non-interacting gas of rubidium atoms (bosons) in external confining potential in a highly excited metastable state. Superfluid is a condensed stable state of a strongly interacting self-bound many body system, made of fermions (e.g. helium-3). BEC can be described microscopically by a simple Hartree-Fock product wave-function. Superfluid has not been described microscopically yet. Of course you are free to call anything BEC/Superfluid/BCS, including the Coulomb field and carbon-12 nucleus, if you wish. It sells at the moment.--Bakken (talk) 21:28, 29 April 2009 (UTC)
 * In my view BEC and superfluid are two completely different and largely unrelated phenomena. Disagree, cf: "In fact, many of the properties of superfluid helium also appear in the gaseous Bose–Einstein condensates created by Cornell, Wieman and Ketterle (see below). Superfluid helium-4 is a liquid rather than a gas, which means that the interactions between the atoms are relatively strong; the original theory of Bose–Einstein condensation must be heavily modified in order to describe it. Bose–Einstein condensation remains, however, fundamental to the superfluid properties of helium-4.".  --Michael C. Price talk 06:07, 30 April 2009 (UTC)
 * "the original theory of Bose–Einstein condensation must be heavily modified in order to describe it" -- have you ever seen this "heavily modified original theory"? Could you give me a reference? :) The idea behind that statement is that the low-energy spectrum of a strongly interacting many-body system can be effectively described as a system of certain quasi-particles (*not* helium atoms) which are weakly interacting bosons confined by the bulk of the liquid. It is those quasi-particles that allegedly form BEC inside a superfluid. Helium atoms do not form a BEC. Especially helium-3 atoms... :) --Bakken (talk) 06:26, 30 April 2009 (UTC)
 * ".... Bose–Einstein condensation remains, however, fundamental to the superfluid properties of helium-4." suggests that BEC and superfluity are not "largely unrelated". Oh, and re Helium-3 However, it was widely speculated that helium-3 could also become a superfluid at much lower temperatures, if the atoms formed into pairs analogous to Cooper pairs in the BCS theory of superconductivity. Each Cooper pair, having integer spin, can be thought of as a boson. During the 1970s, David Lee, Douglas Osheroff and Robert Coleman Richardson discovered two phase transitions along the melting curve, which was soon realized to be the two superfluid phases of helium-3.[2][3]--Michael C. Price talk 07:12, 30 April 2009 (UTC)
 * :) Michael, I know the words, I teach them myself. Think about this: using these smart words, can you calculate the Tc for any realistic superfluid or superconductor? No, you can't, because you don't have the microscopic theory. That's what I mean -- there is no microscopic theory of superfluids or superconductors, only aposteriori phenomenological description. A phenomenological description is not a substitute for a first-principle microscopic theory. --Bakken (talk) 09:09, 30 April 2009 (UTC)
 * And yet that doesn't stop a lot of smart people making the analogy between the Higgs mechanism and superconductivity, between superconductivity and superfluity, and between superfluity and BEC. So I think my original question remains, is the Higgs condensate a form of BEC?  You say "no", but "yes" seems the implication of what a lot of other people say. --Michael C. Price talk 09:43, 30 April 2009 (UTC)
 * :) You just be my guest and join that "lot of other people". However, if you say it is a BEC, you have to indicate what are the non-interacting bosonic particles, that make up your BEC. In the field formulation there are no particles in the Higgs condensate because particles are fluctuations around minimum energy configuration (which is the very condensate), not around *maximum* of the energy. Even if you take the "particle formulation" and claim that there are some hypothetical particles with imaginary mass which can never be observed that *are* the Higgs field, these particles are strongly interacting. In fact so strongly that the very vacuum and the spectrum of the model is completely restructured. Thus these imaginary particles can not make a BEC. The only way for you is to say that the strongly interacting system of original hypothetical imaginary particles can be effectively described as a system of some even more hypothetical non-interacting bosonic quasi-particles. It is those quasi-particles that make your BEC. If you believe that this convoluted reasoning is easier to understand than simply a constant field filling the space -- be my guest, use it. I personally prefer to call a spade a spade... :)--Bakken (talk) 10:31, 30 April 2009 (UTC)

You seem to be implying that the particle formulation has to be constructed by expanding around the origin (Higgs =0). I think you'll find most folks expand around the vacuum, which removes the need to invoke an "imaginary mass". :-) --Michael C. Price talk 12:11, 30 April 2009 (UTC)
 * Please, Michael, ask Likebox, if you don't believe me. If your particles are small fluctuations around the vacuum (the condensate), than your particles are the normal Higgs bosons that people are going to discover at CERN. These particles cannot make Higgs condensate because they are precisely the small deviations from the condensate. Please, Michael, not even Likebox claims that Higgs condensate is made of Higgs bosons. Higgs bosons are unstable particles, they decay in no time. Otherwise we would have found them long ago. Likebox's picture is the one I described above precisely with particles with imaginary mass. There is nothing wrong with those particles in "particle formulation" because these particles cannot be observed, like quarks. The quantities you cannot observe must not necessarily be real. There is nothing wrong with imaginary mass, only that it is ugly, which is a subjective point of view. Likebox believes it is beautiful. --Bakken (talk) 12:34, 30 April 2009 (UTC)

I haven't been following Likebox's description, but I see the point you're making. I thought you were implying that the LHC Higgs would have imaginary mass. Since you're not, that's fine. --Michael C. Price talk 13:29, 30 April 2009 (UTC)

Your recent edits
Hi there. In case you didn't know, when you add content to talk pages and Wikipedia pages that have open discussion, you should sign your posts by typing four tildes ( &#126;&#126;&#126;&#126; ) at the end of your comment. If you can't type the tilde character, you should click on the signature button located above the edit window. This will automatically insert a signature with your name and the time you posted the comment. This information is useful because other editors will be able to tell who said what, and when. Thank you! --SineBot (talk) 22:02, 29 April 2009 (UTC)

Higgs mechanism
I can see that this discussion is degenerating, but I don't understand why we can't agree. What do you have against quarks as particles? The notion that "particle" includes quarks is very old by now.Likebox (talk) 22:55, 29 April 2009 (UTC)

I have nothing against your particle formulation, just leave alone and do not delete the generally accepted formulation from the Particle Data Group.--Bakken (talk) 23:02, 29 April 2009 (UTC)


 * Ok, but then what about the spontaneous symmetry breaking? Surely you agree that the local gauge symmetry is not at all broken.Likebox (talk)


 * Well, the mechanism has been historically called this way, spontaneous symmetry breaking, for decades, don't you agree with that? Of course it is not the Lagrangian, but the ground state that is not symmetric. It might not be the best term, but it is generally accepted and historically belongs to Higgs mechanism. And in my view it is the most concise, precise, and understandable description of the mechanism. If you feel the particle language is better, be my guest, add that formulation, I have nothing particular against it. Only that aesthetically, philosophically, and historically the field formulation is a lot better. The mechanism has always been called spontaneous symmetry breaking, it is still called this name in textbooks and reviews and that has to be reflected in the lead.--Bakken (talk) 23:40, 29 April 2009 (UTC)


 * You just add something like "...however in the modern particle language the term spontaneous symmetry breaking is considered outdated and the Higgs background is rather interpreted as a charged superfluid (which still puzzles everybody) of strongly interacting imaginary-mass particles (and why do they make a superfluid in the ground state? -- only helium does, nobody else) which screens the gauge fields from propagating over large distances...".--Bakken (talk) 23:40, 29 April 2009 (UTC)


 * Thank you for clarifying your thinking, I understand where you're coming from. You are saying that the gauge symmetry is a symmetry of the Lagrangian, but not the ground state, like in Spontaneous symmetry breaking. That's not true for the local part of the gauge symmetry. The local part of the gauge symmetry is a symmetry of the Lagrangian and the ground state no matter what.


 * For the particle business, you should be comfortable with reinterpreting any field phenomenon in terms of particles. This is not difficult--- a constant bosonic field is a coherent superposition of particles making a Bose-Einstein condensate. The classical field is dual to the coherent particle language, and any classical field state of the bosonic field can be viewed as a superposition of coherent particles whose wavefunctions are all the same and given by the classical field. This is explained in the easy non-relativistic case in the article on Schrodinger field. The relativistic case introduces the complication that the particle number is forced to be indefinite, because the particles don't propagate locally, they can go backwards in time.


 * In particle terms, the imaginary mass of the Higgs particles is a tendency to be formed spontaneously from the vaccuum. The particles also repel, by the quartic interaction, when they are on top of one another, so there is a balance: the particles get formed by the imaginary mass, but when there are too many of them, they are too close, and the quartic interaction changes the chemical potential for adding new particles (the field moves), until finally they reach an equilibrium density (the field is constant at a point where its effective potential is minimum). In the lowest energy state, then, you have a fluid of these particles, and their effective mass is now given by small fluctuations of the field.


 * But so far this is the particle picture for ordinary SSB, it's not the Higgs mechanism. In the Higgs mechanism, you have to take into account the fact that the fluid is charged, and that there is a gauge boson, so that the gauge boson becomes short ranged, and the superflows of the condensate are no longer present (they have finite frequency, like plasma oscillations. That's the Higgs mechanism in particle language. If people hadn't understood the particle interpretation from superconductivity, it is not clear that they would have discovered the phenomenon.


 * The symmetry that is broken by the vacuum in the Higgs phase is the global gauge symmetry. The local gauge symmetry is still OK even in the Higgs state. The local gauge symmetry for U(1) says that you can shift A by a gradient of an arbitrary function phi, and rotate the phase of the charged fields by exp(e phi). As long as phi is zero at infinity, this is true whether there is a Higgs mechanism or not, and in fact, using this gauge invariance of the states is the easiest way to calculate the gauge boson mass (that's how its done in the article). The condensate rotates by a phase, the vector potential shifts by a gradient, and the two states are exactly the same state. Nothing changed, even though there is a condensate.


 * The reason is that neither the Lagrangian nor the ground state change at all is because phi goes to zero at infinity. The only way to change the ground state physically is to have a phi which does something at infinity, which is a "global" gauge symmetry. The reason I put "global" in quotes is because the number of global symmetries in a gauge theory is bigger than what is usually called the global gauge symmetry. Not just constant gauge transformation affect the physics, but asymptotically angle-dependent ones too. There is an angle dependent residual of the local gauge symmetries at infinity, this is explained very well in infraparticle. But that's not so important for this discussion, because the angle-dependent asymptotic gauge symmetries can be thought of as "global", while the gauge symmetries that do something only in a local region are the local gauge symmetries.


 * A "charged superfluid" is any boson of spin zero which makes a condensate, not just Helium, which is a neutral superfluid. You don't have any charged bosons made out of protons neutrons and electrons, which is why superconductivity is an exotic phenomenon. To get superconductivity you need to bind electrons together in pairs, and there are no strong forces to do this, because electrons repel. Recently, the idea that nuclei become superconducting inside dwarf stars has been proposed: helium nuclei or carbon nuclei are both bosonic and charged, and if the star is dense enough and cold enough, they might form a superfluid. The moment they do, it's superconducting, and this is the best analog of the Higgs mechanism in ordinary matter.Likebox (talk) 17:00, 30 April 2009 (UTC)


 * If you are interested in the recent thing, it's due to Gabadadze, and he has a recent paper on arxiv in hep-th, just a few days ago. These types of pictures might suggest better ways to compute vacuum structure from what you call "imaginary" particles defined relative to phony vacua. It became important in QCD in the 1980s, though, because Shifman Vainshtein and Zakharov were able to say something real from this type of picture.Likebox (talk) 17:20, 30 April 2009 (UTC)

Your recent edits
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