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Shaposhnikov Wetterich predicted 126 GeV Higgs in 2009

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marcus
#91
Feb15-13, 10:19 AM
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Quote Quote by mitchell porter View Post
The conformal SM is the coolest idea in that list and it's now a working hypothesis for me. ... AS and the CSM have special merits, but the answer could also be None Of The Above.
About the Conformal Standard Model (CSM), which also looks to me like the coolest idea of those four minimalist proposals (!), I want to remind anyone new to the thread that Meissner and Nicolai just recently posted a new CSM paper. They aren't letting the idea drop.

http://arxiv.org/abs/1208.5653
A narrow scalar resonance at 325 GeV?
Krzysztof A. Meissner, Hermann Nicolai
(Submitted on 28 Aug 2012, last revised 20 Sep 2012)
We propose to identify the excess of events with four charged leptons at E ≈ 325 GeV seen by the CDF and CMS Collaborations with a new 'sterile' scalar particle characterized by a very narrow resonance of the same height and branching ratios as the Standard Model Higgs boson, as predicted in the framework of the so-called Conformal Standard Model.
4 pages, 2 figures. Phys.Lett. B718 (2013) 943-945

I'll also expand the reference to their 2007 CSM paper you gave in post #88:

http://arxiv.org/abs/hep-th/0612165
Conformal Symmetry and the Standard Model
Krzysztof A. Meissner, Hermann Nicolai
(Submitted on 15 Dec 2006, last revised 26 Mar 2007)
We re-examine the question of radiative symmetry breaking in the standard model in the presence of right-chiral neutrinos and a minimally enlarged scalar sector. We demonstrate that, with these extra ingredients, the hypothesis of classically unbroken conformal symmetry, besides naturally introducing and stabilizing a hierarchy, is compatible with all available data; in particular, there exists a set of parameters for which the model may remain viable even up to the Planck scale. The decay modes of the extra scalar field provide a unique signature of this model which can be tested at LHC.
13 pages, 6 figures. Phys. Lett. B 648, 312 (2007)
mitchell porter
#92
Feb19-13, 08:20 PM
P: 755
I am peeved today, to see a flood of science journalism talking about "Higgs calculations show universe may end", with an anthropic tag-along saying "and maybe the Higgs mass was tuned so the universe would last just long enough to produce observers". There is a dismaying possibility that this new anthropic dogma will get most of the attention, even within physics, at the expense of attempts at causal explanation.
atyy
#93
Feb19-13, 08:23 PM
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Quote Quote by mitchell porter View Post
I am peeved today, to see a flood of science journalism talking about "Higgs calculations show universe may end", with an anthropic tag-along saying "and maybe the Higgs mass was tuned so the universe would last just long enough to produce observers". There is a dismaying possibility that this new anthropic dogma will get most of the attention, even within physics, at the expense of attempts at causal explanation.
It was worth it to hear in the comments that Mexico will outlast the universe, because the end of the universe will come at the speed of light, but in Mexico light is much slower, sometimes taking an infinite time to arrive after the switch has been flipped.
typical guy
#94
Feb19-13, 09:28 PM
P: 22
I feel stupid every time I receive an answer to one of my questions but I continue to ask them anyway. So here goes:

1. Assume SOMEWHERE in the unobserved portion of the universe, a bubble forms (the new ground state discussed in this thread) and expands outwards at the speed of light. Will the bubble EVER reach us? In other words, the universe is expanding at an accelerating rate, possibly faster than c. If so then won't this bubble be constantly converting new space that's stretched?

2. Assuming that the universe would never be completely converted by the bubble, would other bubbles eventually form? A follow up, would these bubbles have the same exact ground state as one another and if not, what happens if they form close to one another and eventually collide?

3. Assuming that the universe is expanding too quickly for the bubble(s) to catch up with us, does that imply that previous higher energy states of the universe might be "laying around" somewhere expanding outwards so quickly that our spacetime cannot possibly eat it/them all away?

Thanks in advance and apologies if this has been asked before or if these questions seem stupid.
mitchell porter
#95
Feb19-13, 09:48 PM
P: 755
typicalguy, you seem to have the right ideas - an instance of vacuum decay can't spread beyond the cosmological horizon of the point where it began, but any part of the universe that is in a false vacuum state is at risk of locally experiencing vacuum decay.

Other threads might be better for a general discussion of this issue (whether the Higgs field is in a false vacuum state, and the consequences if it is). If we discuss it further here, it should be specifically in the context of Higgs mass predictions like the one in the title.
mitchell porter
#96
Feb19-13, 09:55 PM
P: 755
And there is something for SW fans to talk about here. In all our discussion we have hardly alluded to the fact that the SW prediction is on the boundary between stable vacuum and unstable vacuum. But it's not a coincidence; the vacuum instability occurs if the Higgs quartic coupling becomes negative at any scale, and the SW boundary condition is that the Higgs quartic coupling is zero at the Planck scale. So, it's right on the edge.

But I for one don't feel like I have a proper understanding of this. Is there some deep reason to expect that a quantum-gravitational mechanism for determining the Higgs mass would drive it to a metastable value?
marcus
#97
Feb19-13, 11:56 PM
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Quote Quote by mitchell porter View Post
typicalguy, you seem to have the right ideas - an instance of vacuum decay can't spread beyond the cosmological horizon of the point where it began, ...
typicalguy just for concreteness the distance to the horizon is currently around 15.7 or 15.8 billion ly.

I'm not sure such bubbles are able to form, but if they can, and one did, say 16 billion ly from us, today, then the effects could never reach us. for the reason you mentioned, accelerated expansion, out of causal range.

this calculator gives the past and future development of the cosmological event horizon (CEH):
http://www.einsteins-theory-of-relat...TabCosmo6.html

The CEH is slated to gradually increase and converge to around 16.5 billion ly, as can be seen in the calculator's table output.
Haelfix
#98
Feb20-13, 01:05 AM
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P: 1,685
Whether the vacuum is stable, metastable or unstable has very little to do with details about quantum gravity, and almost everything to do with the exact value of the top quark mass and the mass of the Higgs. See figure 5

http://arxiv.org/pdf/1205.6497v1.pdf

Now, if you can find some unification proposal that links gravity to those two values (which I assure you everyone and their mother is trying to do right now), then be my guest, but right now it looks very much like its some sort of coincidence. I hate to use the A word, but well there's that too.
mitchell porter
#99
Feb20-13, 08:00 AM
P: 755
Well, arivero likes to point out that the top yukawa is very close to 1. Though it is closest at low energies, if I am to believe Figure 7 (page 14) here. So all we need is a reason for the Higgs self-interaction to be zero in the far UV, some wacky UV/IR reason for the top yukawa to be almost 1 in the far IR, and we're done. :-)
mitchell porter
#100
Mar7-13, 08:13 PM
P: 755
This paper, before it gets around to introducing its new model of BSM physics, actually states the case for a "desert" in some detail:
Quote Quote by arxiv:1303.1811
The standard model (SM) is extremely successful at predicting what we do not see - namely flavor changing neutral currents (FCNC), lepton family violation among charged leptons, proton decay or neutron oscillations, and (with the exception of the strong CP problem) large CP violating e ffects. These all follow from the fact that such processes require irrelevant operators in the SM and are therefore suppressed by the high energy scale associated with new heavy particles. By assuming a desert for many decades of energy above the electroweak scale, all of the above processes are strongly suppressed, providing a simple explanation for what we (don't) see...

There is tension in the SM, however, between the natural explanation of a desert for the absence of FCNC, lepton and baryon number violation, and CP violation on the one hand, and the fi ne tuning of the Higgs sector that comes with a desert on the other.
In other words: a desert is the natural explanation for why we don't observe many phenomena which otherwise ought to be possible; but then the Higgs appears to be finetuned... All the more reason, therefore, to take seriously those desert models which would provide a causal explanation of this finetuning.
mitchell porter
#101
Mar19-13, 06:19 PM
P: 755
Via Peter Woit, a talk by Joseph Lykken reviewing a number of non-susy approaches to explaining the tunedness of the Higgs mass. (Woit also links to a more theoretical talk by Nathan Seiberg about the hierarchy problem, that is also worth reading.)

It seems that causal explanations of the tuned Higgs, like Shaposhnikov-Wetterich and Nicolai-Meissner, are beginning to be recognized as a distinct class of theory, alongside "unnatural" and/or anthropic finetuning (Arkani-Hamed) and new versions of SUSY which restore naturalness (numerous authors). This is heartening, and it's especially gratifying to see Lykken at the fore of this, since it was his soundbite about the metastability of the universe, and the flurry of media it generated, which prompted my dismay in comment #92.

In fact, Lykken not only reviews several possibilities, but he devotes the most attention to a model in which dark matter plays a role in a Nicolai-Meissner-like mechanism. That is, he combines "radiative electroweak symmetry breaking" - in which the destabilizing Mexican-hat self-interaction of the Higgs field (that is responsible for a ground state with a nonzero VEV, and thus for the Higgs mechanism) is induced by virtual effects - with high-energy boundary conditions that tune the resulting Higgs mass. In this model, the new particle which induces radiative EWSB is also the dark matter!

So not only are causal models of Higgs tuning beginning to be recognized, but they are being combined with BSM facts from elsewhere in physics. Perhaps this will even become a popular topic while we wait for the LHC to be switched on again...

edit: What would really be dramatic, is a model of a "causally tuned Higgs" which also explains the observation that the mass of the Higgs is half the sum of the Z, W+, and W- masses. Like the tuning of the Higgs mass, this isn't just something that was noticed after the discovery, it was actually used to predict the correct value. Unfortunately, the "theory" which produced that formula is nonsensical, so the formula really needs some other justification.

Also, like the Koide relation, it's a relation between low-energy masses which shouldn't have simple relations, because of renormalization group running. (This may be contrasted with theories like Shaposhnikov-Wetterich, where the low-energy Higgs mass acquires its value from a simple boundary condition at high energies.) So most physicists will dismiss it as numerology and a coincidence. But as Lykken says in his talk (slide 20), "dismissing striking features of the data as coincidence has historically not been a winning strategy..."
the_pulp
#102
Sep27-13, 06:50 PM
P: 138
Look at this conference http://workshops.ift.uam-csic.es/WMH126/program.html at which Shaposhnikov participated and look in particular his pdf and video. It is more or less what he stated in his 2009 paper + some other papers that he wrote.

However, even though it sounds as the same conclusions, here he talks about a desirable mass of 129 Gev and not of 126 Gev, so here, the agreement with experiments (LHC) is not so good now. Do you know what changed in the estimation of this "optimal mass" between 2009 and 2013 that moved the number in 3 Gev?
MTd2
#103
Mar13-14, 08:16 AM
PF Gold
P: 1,961
http://arxiv.org/abs/1205.2893v2

It seems 129+-6GeV.

There is a discussion about fit with a higgs cosmology here and the value of Higgs:

http://arxiv.org/abs/1311.4979


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