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The Higgs mechanism and the Beginning of the Universe 
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#1
Jul2312, 10:04 AM

P: 175

Now that the excitement about the discovery of the Higgs particle has made the Higgs
mechanism justly famous, could someone please clarify for me the implications of incorporating this component of the Standard Model of Particle Physics into the Standard Model of Cosmology? As (hopefully) I understand it, the Higgs mechanism is thought to be instrumental in assigning mass to stuff, firstly to matter made of Fermions, which do have a restmass (mass measured at rest relative to an inertial observer) and secondly to Bosons, that don’t have a rest mass and are therefore, according to special relativity that rules locally, always travelling at lightspeed, c. But Bosons do carry energy and so acquire relativistic mass, which has inertia, gravitates and qua mass, must also be assigned by the Higgs mechanism. Is this correct? I also understand that the Higgs mechanism is thought to have first switched on suddenly, as it were, in the cooling and expanding veryearlyindeed universe, when a phasechange was caused by the spontaneous symmetry breaking of a specific potential. Before this instant, in what I’d like to call the dawn universe, mass had not yet emerged into existence as something that could be measured, even in principle by imaginary inertial observers. Indeed, in such a dawn universe the presumably entirely inertia and massless (but today massive) particles/waves that comprise the material universe, namely Fermions and Bosons, must then have all been (locally) travelling at c. It seems to me that the time dilation of special relativity tells us that time itself, as we know it, must then have been on hold, as it were, and that it could not then have existed as a locally measurable parameter for local physics, even in principle. If all this is not mistaken perhaps Eternal Dawn would be a more appropriate description of the Beginning than Big Bang. 


#2
Jul2312, 11:57 AM

Astronomy
Sci Advisor
PF Gold
P: 23,228

Things are speculative at this point. I will quote an excerpt from a post I wrote yesterday in another thread:
==quote== Higgs inflation in Loop cosmology is the topic of a new paper that just appeared and impressed me as potentially important. It's by Tom Pawlowski, a postdoc at Warsaw, and two PhD students there: Andrea Dapor and Michal Artymowski. It puts inflation in a new light for me. So I expect some rapid development in this area: http://arxiv.org/abs/1207.4353 Inflation from nonminimally coupled scalar field in loop quantum cosmology Michal Artymowski, Andrea Dapor, Tomasz Pawlowski (Submitted on 18 Jul 2012) The FRW model with nonminimally coupled massive scalar field has been investigated in LQC framework. Considered form of the potential and coupling allows applications to Higgs driven inflation. The resulting dynamics qualitatively modifies the standard bounce paradigm in LQC in two ways: (i) the bounce point is no longer marked by critical matter energy density, (ii) the Planck scale physics features the "mexican hat" trajectory with two consecutive bounces and rapid expansion and recollapse between them. Furthermore, for physically viable coupling strength and initial data the subsequent inflation exceeds 60 efoldings. 14 pages, 5 figures Here are links to earlier papers by Bezrukov and Shaposhnikov http://arxiv.org/abs/0710.3755 (209 cites) The Standard Model Higgs boson as the inflaton http://arxiv.org/abs/0904.1537 (78 cites) Standard Model Higgs boson mass from inflation: two loop analysis The latter was cited by ADP... ==endquote== Loop cosmology is one approach to understanding the early universe that is being worked on a lot and may in future be tested by observations. In this model, time extends back before the start of expansion. There is a collapsing phase that rebounds due to quantum effects ("big bounce"). There is a brief episode of superinflation caused by the bounce and then ordinary inflation might take overpossibly driven by the Higgs field. That is the possibility that these authors Artymowski Dapor Pawlowski (ADP) are studying. At the end they offer some ideas as to how the type of bounce and expansion they are talking about could be TESTED by looking for specific traces of it in the cosmic background radiation. This work is clearly preliminary and speculative. I expect to hear more about it in the coming months. 


#3
Jul2312, 03:12 PM

P: 5,632

Paulibus:
It seems there are dozens of 'Higgs fields" to accompany dozens of particle characteristics. My limited understanding is that IF CERN has discovered a Higgs particle they don't know which 'one' [or ones] yet. Higgs fields get stuck in the Standard Model by hand...slick mathematical tools to create desired, observed characteristics. Like the rest of the Standard Model, lots of pieces but exactly why they fit is not so clear and there are still lots of pieces that have to be added ad hoc to match what we observe. I happen to be reading Alan Guth's THE INFLATIONARY UNIVERSE at the moment and he describes what he did, how he got there, and the available information when he 'invented' the cosmological 'inflation', exponential expansion, that has become so popular. Guth and his main collaborator [Henry Tye] were working on the magnetic monopole problem...why we observe none. John Preskill beat them defining the problem mathematically with his paper and so Guth decided to work on a method to theoretically avoid magnetic monopoles. The issue was "why are so many magnetic monopoles predicted yet we observe none?" What circumstances would be compatible with a hot big bang?.... and avoid magnetic monopoles....fast symmetry breaking did not make magnetic monopoles to disappear.....but some appropriate expansion would....hmmm....He knew about phase transitions and spontaneous symmetry breaking in 1979 and from Sidney Colemans 1977 paper THE FATE OF THE FALSE VACUUM'. [False meaning temporarily at an elevated vacuum energy density ] He knew from GR that such a false vacuum leads to gravitational repulsion. It seems he also rediscovered the de Sitter solution to EFE before later finding that Lemaitre had already done that in 1925....skunked again!!!...BUT all was not lost...he had all these pieces hanging around...[reminds me of all the pieces Einstein had when developing SR [ether?, fixed speed of light?, Lorentz contraction, Fitzgerald time dilation, etc....] Anyway, a false Higgs vacuum, as a scalar field would give him the characteristic delay he needed to allow expansion to continue long enough to give him the expansion he sought to dissipate magnetic monoples from existence.....gluing these pieces together, Volia!!! inflationary expansion was born!! After realizing this and confirming with some calculations, THEN he realizes such extended rapid expansion also solves the flatness problem he had heard about a year before in a talk he attend given by Dicke.....Apparently he had not known about THAT issue peviously but was smart enough to realize it 'fit' his expansionary ideas.....but his model had not planned to incorporate that fantastic and necessary result...it was a 'freebe'. I still find it amazing that nature fits some of our math. 


#4
Jul2312, 04:11 PM

Astronomy
Sci Advisor
PF Gold
P: 23,228

The Higgs mechanism and the Beginning of the Universe
This is the simplest outcome, there ARE other possible Higgs or Higgslike fields which if they had NOT found this one they could now be theorizing about and looking for. Matt Strassler's blog "Of Particular Significance" has several tutorials about this. But it's highly probable that the situation has begun to simplify. What LHC found probably is indeed the SM Higgs. Guth was born February 1947, so he turned 65 a few months ago. How he happened on the inflation hypothesis around 1980 is an interesting human interest story! My hunch is that we are entering a new phase of understanding the early universe  inflation scenarios in particular. This 2007 paper could be a key one: Bezrukov and Shaposhnikov http://arxiv.org/abs/0710.3755 (209 cites) The Standard Model Higgs boson as the inflaton Back in 1980 Guth and Linde were talking about a dreamed up inflaton field and a lot features of the scenario were based on exotic made up stuff that nobody had ever seen. Now we have a possibility of modeling inflation with a particle we actually know about and have seen at CERN. But notice that the Pawlowski paper gets a more general result. They explicitly say they're good with Loop bouncefollowedbyinflation for a wide range of scalar fields. If it is this 125 GeV Standard Model Higgs fine and dandy! But it would work with a bunch of other similar fields (nonminimally coupled massive scalar), if that one somehow drops out of the picture and LHC finds something else. http://arxiv.org/abs/1207.4353 Inflation from nonminimally coupled scalar field in loop quantum cosmology Michal Artymowski, Andrea Dapor, Tomasz Pawlowski (Submitted on 18 Jul 2012) The FRW model with nonminimally coupled massive scalar field has been investigated in LQC framework. Considered form of the potential and coupling allows applications to Higgs driven inflation. The resulting dynamics qualitatively modifies the standard bounce paradigm in LQC in two ways: (i) the bounce point is no longer marked by critical matter energy density, (ii) the Planck scale physics features the "mexican hat" trajectory with two consecutive bounces and rapid expansion and recollapse between them. Furthermore, for physically viable coupling strength and initial data the subsequent inflation exceeds 60 efoldings. 14 pages, 5 figures ===quote from page 1 of ADP paper=== At this point it is worth noting that the type of the potential considered, while usually associated with the models of Higgs inflation, is not restricted just to this particular field. In fact, our studies can be easily (generalized and) applied to the analysis of the inflation driven by any nonminimally coupled scalar field with realistic values of ξ and λ. ==endquote== 


#5
Jul2412, 02:06 AM

P: 6,863

The problem is that you have bosons without mass (i.e. photons). Bosons with mass (the W and Z particle). You would *like* to get photons and W/Z particles into the same "beautiful" theory. In order to do that, if you assume that the Higgs field exists and interacts with W and Z particles but not photons, then you end up with a nice elegant theory. Note, here that we are talking all about "rest masses". "Relativistic mass" is a way of explaining special relativity that turns out to cause more confusing than anything else. Since Higgs is a nice mechanism for giving W and Z particles mass, people sort of assume that the same mechanism would work for all particles, but that's not been established yet. 


#6
Jul2412, 02:20 AM

P: 6,863

Today, I don't think that people believe that inflation really solves the monopole problem because it's not clear that there is a monopole problem to begin with. Now there are *other* reasons for thinking that inflation exists, and one of the stronger results for thinking that there is inflation (i.e. gaussian flucutations) is something that no one who thought of inflation originally had thought of. . And then there is Christopher Columbus and America. For that matter one of the major discoveries made at CERN was the world wide web. 


#7
Jul2412, 02:31 AM

P: 6,863

Here is another paper
http://arxiv.org/pdf/1003.2635.pdf The interesting thing about this paper is that it explains why most people for the longest time assumed that the Higgs field could *not* be the inflation field. Trying to translate this into English. The original result is that if you assume that the Higgs particle causes inflation then the Higgs field is strong enough so that you can't get it to work without assuming quantum gravity effects. What the new papers are saying is "well, let's make some lemonade, assume that the Higgs particle causes inflation and then assume some things about quantum gravity." 


#8
Jul2412, 04:52 PM

P: 5,632

But the story Guth tells so far in his book and I attempted to capsulize above includes a 'false Higgs vacuum' decay which does provide a plausible end to inflation. I haven't finished the book yet so there may be more to the story. According to his recollection of this effort so far, he had to do some calculations to verify the phase transition delay was long enough to smear out monopoles...turns out it he thought so ... 


#9
Jul2412, 05:02 PM

P: 5,632

I had recently read somewhere the CERN team was not sure which Higgs particle they had discovered and it would be some months before they figured that out so I have not being paying any attention so far. But I imagine they are being especially cautious after the recent 'faster than light discovery' proved otherwise. 


#10
Jul2512, 03:45 AM

P: 175

Thanks, Marcus, for the references. And for the comment "My hunch is that we are entering a new phase of understanding the early universe  inflation scenarios in particular." I agree and hope you're right. And thank you, Naty1, for your posts and remarks about multiple Higgs'. I hope you are overly pessimistic!
I'll reply specifically to your kind detailed and specific clarifications, and corrections about W and Z, twofishquant: But perhaps I'm wrong, and in that case I'd like to be corrected. About the implications for cosmology of the newly discovered Higgs, the one CERN's Heuer announced on July 4: definitely profound; imagine running the evolution of the universe as a movie backwards (dynamics is timesymmetric, remember) until one comes to the proposed instant when the Higgs mechanism (and possibly inflation?) switched on at an appropriate and inconceivably high temperature. Suddenly, no more mass/energy, inertia or gravity! I suggest that here local time loses its meaning as a useful parameter with which to describe reality, which is the task of physics. Hence the end (or rather the beginning) of our subject. Perhaps a universewide time could still exist, to be measured from the blackbody temperature of radiation, as we run the movie even further back? The scope for speculation here has enormous potential to keep shoals of theoretical physicists employed far into the future! I vote for Anderson, Higgss and CERN as the next three recipients of the Nobel prize. 


#11
Jul2512, 10:21 PM

P: 6,863

The Higgs mechanism is solely to generate "rest mass". It's got nothing to do with generating inertia in general or gravity. One way of thinking of "symmetry breaking" is to imagine an 1 kg of apple and 1 kg of glass of water and 1 kg of lead. They act pretty differently. Now if you heat the apple and glass of water to 5000 celsius, they are going to start behaving the same way. If you heat them to 10 million celsius, they are going to behave exactly the same. At 10 million celsius apples, water, and lead just become particle plasma with exactly the same characteristics. Similarly W,Z and photons are very different at low temperatures. Heat it up to GUT temperatures and they act the same. If you heat apples to extremely high temperatures, there will be some temperatures at which the characteristics of the apples change, but this doesn't cause any "weird stuff" to happen with time and space. The energy at which we expect "something weird" to happen with time and space is much, much hotter than the Higgs symmetry breaking temperatures. 


#12
Jul2512, 10:32 PM

P: 6,863




#13
Jul2612, 01:26 AM

P: 175

Thanks for this clear and definite reply, twofishquant. Seems as if I've been harbouring delusions. Just one last delusion to be considered, perhaps.
I thought that gravitational mass, inertial mass and energy were all truly and fully equivalent; for example that a hot gas weighed more than the same gas cold, because the mass equivalent of the extra particle kinetic energy gravitated, and likewise that a stretched spring weighed more than the same spring unstretched, because its stored elastic energy gravitated. Also that the hot gas and stretched spring would both be accelerated less by the firing of identical standardised rockets attached to them, than would their cold and unstretched counterparts, with less mass and therefore less inertia. You seem to be telling me that this is wrong. Is it? I feel sand shifting below my feet! 


#14
Jul2612, 03:22 AM

P: 6,863

It's the "particle rest mass" that is generated from the Higgs field. The other ways that you can get gravity and inertia have nothing to do with Higgs. And yes this means that "particle rest mass" is "different". Also, if you aren't the curious sort, you *could* say that particles have mass "just because". However that looks messy to physicists, so they want to put the known particles into a nice symmetric theory. So you write the equations for the Higgs field which are nice and symmetric and short. When you lower the temperature and then the equations get messy, but you end up with "rest mass" for the weak bosons and a particle with zero rest mass which is the photon. You also get several other particle interactions that we can observe. One other way of thinking about this. There is particle behavior that you get from things moving around. This is "easy" to write a simple equation for. If you had zero mass particles moving around, and all of the inertia and gravitation came from "energy of motion" there wouldn't be any need to add a Higgs field. The trouble is that if you take a particle and then just freeze it, some of them still have "mass" and then you just end up adding random things to your equations. By adding one Higgs field, you end up with an equation that gives you "rest mass" without saying "just because." 


#15
Jul2612, 04:53 AM

P: 175

Thanks for the prompt reply. I'm becoming more and more reminded of 1984 in which George Orwell coined the word doublespeak, despite your kind and valiant attempts to explain to simple me in simple language what the Higgs does for rest mass, but not for mass in the form of energy. Some mass is more equal than other mass? (shades of Orwell again). eems to me a strange proposal .
You've said: 


#16
Jul2612, 07:20 AM

P: 526

What are you talking about? The Higgs field generates the rest mass of particles by interacting with them (called a Yukawa interaction). In SR, observers disagree on the amount of mass of an object due to Lorentz transformations. Where do you see a contradiction?



#17
Jul2612, 09:08 AM

P: 175

Mark M: No contradiction seen. What happens if the Higgs hadn't yet operated, as in the very early universe before the Higgs scalar field symmetry was spontaneously broken? No rest mass, no mass for observers to disagree about? Read the rest of the thread before you rush to post a twoliner, please.



#18
Jul2612, 09:29 AM

P: 526

http://math.ucr.edu/home/baez/physic...oton_mass.html 


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