Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Vacuum Metastability

  1. Mar 23, 2018 #1
    14myE5.jpg

    What is the best theory why our vacuum may be in the edge of metastability?

    Is it possible there are many false vacuum separated by energy barriers and the reason why our vacuum may be metastable is so that it is easier to cross the different false vacua (not necessarily to the true vacuum)?
     
  2. jcsd
  3. Mar 24, 2018 #2

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    It's got to be somewhere.
     
  4. Mar 25, 2018 #3
    Here may be a simpler question related to it. I read in Deep Down Things that:

    "What is the physical origin of the external Higgs potential? What is the physical basis of the peer pressure–like internal organizing principle that causes the Higgs field symmetry to be hidden in a uniform manner throughout space-time? These questions, unanswerable within the Standard Model, suggest that, beyond the unearthing of the Higgs boson, there may well be some radically new facet of the natural world awaiting our discovery."

    So far what are the existing proposals of the physical origin of the external Higgs potential? How related is it to the vacuum metastability?
     
  5. Mar 25, 2018 #4

    ohwilleke

    User Avatar
    Gold Member

    The underlying premise of the question, it is worth noting, isn't on entirely solid ground.

    It would only take the slightest of tweaks to the renormalization group of the Higgs (or including some slight usually overlooked and ignored nuance of the calculation that the metastable result relies upon) from BSM physics to nudge the universe from merely metastable to stable.

    For example, the SM + quantum gravity, or a singlet dark matter particle with a Higgs portal, might cause such a slight tweak. The asymptotic gravity prediction of the Higgs boson mass that is now so famous, for example, included a quantum gravity adjustment to the renormalization of the Higgs with energy scale.

    There is also a fair amount of imprecision in the top quark mass (in absolute terms even though the percentage uncertainty isn't that huge) that could give the stability-metastability question a nudge one way or the other. Probably not enough to cross the line by itself, but enough to make the necessary BSM tweak even more subtle.
     
  6. Apr 1, 2018 #5

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    You all should provide citations for claims you make or refer to, lest the discussion becomes arbitrary.

    For the record: The plot from the original question in #1 is taken from

    Giuseppe Degrassi, Stefano Di Vita, Joan Elias-Miró, José R. Espinosa, Gian Giudice, Gino Isidori,
    "Higgs mass and vacuum stability in the Standard Model at NNLO",
    J. High Energ. Phys. (2012) 2012: 98 (arXiv:1205.6497, doi:10.1007/JHEP08(2012)098)

    This computation has meanwhile been refined in

    A. V. Bednyakov, B. A. Kniehl, A. F. Pikelner, and O. L. Veretin,
    "Stability of the Electroweak Vacuum: Gauge Independence and Advanced Precision",
    Phys. Rev. Lett. 115, 201802 (arXiv:1507.08833, doi:10.1103/PhysRevLett.115.201802)

    where the result is plotted like so:

    HiggsVacuumStabilityII.png

    An expository summary of this result appeared in

    Alexander Kusenko,
    "Are We on the Brink of the Higgs Abyss?",
    Physics 8, 108 (2015)

    which concludes as follows:

    "[The] conclusion is that the best theoretical fit to measured parameters, including the Higgs and top-quark masses, points to a metastable Universe. However, their analysis also concludes that values of parameters are closer to a region of absolute stability than suggested by previous studies: it is possible for the Universe to be fully stable (and for the standard model to work all the way up to the Planck scale), if the true values of measured parameters are only 1.3 standard deviations away from the current best estimates."

    In view of this, it seems to me that the question in #1 as phrased does make good sense: According to available data the observed Higgs vacuum is indeed very close to the edge of metastability. This necessarily brings with it that it is uncertain on which side of this edge we are, but that was not the question.
     
    Last edited: Apr 1, 2018
  7. Apr 1, 2018 #6

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    One argument that I am aware of is the following:

    A number of references argue that Higgs vacuum instability is in fact incompatible with cosmic evolution, as due to vacuum fluctuations during inflation the vacuum decay would not have been avoided (EGR 07, EEGHR 09, HKSZ 14, EGMRSST 15, EKSYZ 16) unless a further mechanism served to prevent it. That supersymmetry provides such a mechanism has been argued in (BDGGSSS 13, section 7, Kane 18 , “Clue 4”).
     
  8. Apr 2, 2018 #7

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    As Philip Gibbs kindly points out to me, he was maybe the first to highlight the core of these points and arguments way back in 2011, right before the official announcement of the Higgs detection:

    Philip Gibbs,
    "What would a Higgs at 125 GeV tell us?",
    in "Seminar Watch (Higgs Special), Rumoured Higgs at 125 GeV and What Would a Higgs at 125 GeV Tell Us?",
    Prespacetime Journal, December 2011, Vol. 2 Issue 12 pp. 1899-1905 (web)
     
    Last edited: Apr 3, 2018
  9. Apr 3, 2018 #8

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    It is also interesting to note how the precision analysis of Bednyakov et al 15. seems to invalidate the now famous suggestion by Shaposhnikov-Wetterich 09 (which was motivated from the principle of "asymptotic safety") that the beta function ##\beta_\lambda## for the quartic Higgs self-coupling ##\lambda## should vanish asymptotically. According to their precision plot (p. 17-18) it does not asymptotically vanish at all:

    HiggsQuarticBetaFunctionRelative.png
     
  10. Apr 3, 2018 #9
    Thanks for the paper. It explained a lot.
    However, is there no mathematical or theoretical possibility for there to be new physics that doesn't affect the Higgs coupling or Higgs potential? Or are they all categorically related. Perhaps some new forces of nature didn't have any virtual particle contribution at all? With regards to this paragraph:

    "If the LHC finds Higgs couplings deviating from the SM prediction and new degrees of freedom at the TeV scale, then the most important question will be to see if a consistent and natural (in the technical sense) explanation of EW breaking emerges from experimental data. But if the LHC discovers that the Higgs boson is not accompanied by any new physics, then it will be much harder for theorists to unveil the underlying organizing principles of nature. The multiverse, although being a stimulating physical concept, is discouragingly difficult to test from an empirical point of view. The measurement of the Higgs mass may provide a precious handle to gather some indirect information"

    Up to what TeV before we can say that there is no physics at the TEV? Is it 1 TeV? 10 TeV? 100?

    And does it always have to involve energy.. for example.. general relativity was a new physics last century that didn't involve TeV.


     
  11. Apr 3, 2018 #10

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    Just out of interest: I take that to mean that you did not get the plot in your message #1 from that paper? Where did you get it from?
     
  12. Apr 3, 2018 #11
    I used yahoo.com.. type "vacuum metastability" and several dozens of images came up. I chose the clearest picture.
     
  13. Apr 3, 2018 #12

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    I find it hard to tell what you are asking here, as it sounds a little garbled. You should be asking whether the renormalization group flow of the Higgs self-coupling to the Planck scale as shown here is computed with the assumption that there is no new physics in between the weak scale and the Planck scale (called the "great desert" assumption). And the answer to that is: Yes.

    And then the logic turns around: Since under the "great desert"-assumption the RG flow is seen to run at least extremely close to the point where the Higgs vacuum would become unstable, one may argue that this assumption must be wrong, and that there should be some new physics kicking in, which prevents that. Such as, possibly, supersymmetry or something else. This is not a solid proof, of course, but that's the kind of plausibility argument usual in phenomenology.
     
  14. Apr 3, 2018 #13
    In the same paper.. if there were this "new scalar field, non-minimally coupled to gravity the slows down the inflationary phase".. is it possible it is new physics but doesn't belong between the weak scale and planck scale.. it other words, can new scalar field exist that doesn't have a corresponding particle? remember we are not even sure gravity has gravitons. So generally could any new physics occur that doesn't belong between weak and planck scale? Nature may use very exotic organizing principles that is not naturalness, multiverse, sabine cosmic lotto, etc.

    "If the Higgs field is trapped in the false vacuum during the early universe, it can cause inflation. The normalization of the spectrum of primordial perturbations, which is determined by Vmin, can be appropriately selected by tuning the ratio λ∗/b. The main difficulty of this scenario is to achieve a graceful exit from the inflationary phase. Two mechanisms have been proposed. The first one [24] employs a new scalar field, non-minimally coupled to gravity, that slows down the expansion rate, thus allowing for quantum tunneling of the Higgs out of the false vacuum. The second mechanism [25] uses a scalar field weakly coupled to the Higgs which, during the cosmological evolution, removes the barrier in the Higgs potential in a process analogous to hybrid inflation. So, in practice, the minimality of the SM is lost and one may wonder if there is any conceptual gain with respect to adding a new scalar playing the role of the inflaton. Nevertheless, it is interesting to investigate whether the Higgs and top masses are compatible with the intriguing possibility of a false vacuum at large field value."

     
  15. Apr 3, 2018 #14

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    jtlz, you are rambling now in a non-educated way. What is it that you actually want to know?
     
  16. Apr 3, 2018 #15
    In more technical term. New physics can affect the computation of the renormalization group flow of the Higgs self-coupling to the Planck scale but what if that new physics was more fundamental than QFT or something where QFT and gravity were emergent. So my inquiry was whether it is possible to have new physics that is not in between the weak scale and planck scale but outside of them.

    In other words. There may be a simpler alternative to multiverse from Occam razor and it is that the organizing principles of nature is simply because they were made that way. So the new physics may be related to the causal mechanism behind the scene or behind our Standard Model.. meaning any new physics can be independent of Higgs coupling or Higgs potential and the virtual particles. For example Microsoft programmer can rewrite the program in different ways (using C or Fortran or newer version) without our commercial Windows software being affected. May I know what is the official language for this description of other ways to have new physics in our current theoretical physics?
     
  17. Apr 3, 2018 #16
    What I meant is. Our constants of nature is so incredibly fined tuned. The following are the possibilities:

    1. Naturalness (like Calabi-Yau where the constants could be in the form of moduli, etc.)
    2. Multiverse
    3. One universe but constants chosen like Lotto Win

    Right now we have utter division in the field with Sabine and company into the third and many into second and the others into the first possibility. Isn't it legit to have other possibilities like our constants of nature were designed and only one universe. So it's either the designed used specific calabi-yau shapes chosen at Big Bang or other new physics that guide them. I was asking if there is official name for this new physics that guide them. Something along the line of perhaps actual implementation of AdS/CFT? Right now it's just toy model because it is not our spacetime. Could there be new implementation where it can use our spacetime. Or similar to the concept. This is the context of my question. Our constants of nature are incredibly fined tuned we need to think of all possibilities. Hence my question are not rambling in non-educated way but reflect the great division now going on in theoretical physics and the confusion (This is the theme of Sabine new book coming soon).
     
  18. Apr 3, 2018 #17
    I just read http://backreaction.blogspot.com/ where Sabine reviews the book "Farewell to Reality: How Fairytale Physics Betrays the Truth for Scientific Truth".

    Sabine doesn't believe in naturalness or supersymmetry or even Multiverse. She reasoned seemingly fined tuned stuff like the vacuum metastability just happens (like winning lotto) without formula because there is no Bayesian background. But I found her belief even weirder. So what if all of them are wrong and there should be other options. That's all. Hierarchy problem, vacuum metastability if confirmed were just too strange especially if there was no naturalness, no supersymmetry, no multiverse.. and Sabine model of cosmic lotto doesn't work (someone correct me if I got Sabine position wrong but I think's that's the contents of her book "Lost in Math".)
     
  19. Apr 3, 2018 #18

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    One option is missing:
    • Having a theory that explains the numbers.
    "The arguments based on ‘naturalness’ are basically like saying the weather tomorrow should be the same as today. The opposite of naturalness is having a theory. […] It would have been nice if the naturalness arguments had worked, but they did not. Since they were not predictions from a theory it is not clear how to interpret that. [...] The failure of naïve naturalness to describe the world tells us we should look harder for a theory that does [work at high energies], an ‘ultraviolet completion’. [...] The alternative to naturalness, often neglected as an alternative, is having a theory." (Kane 17)

    If you just think about it, you will realize that the universe is full of extreme ratios and hierarchical scales. Say the radius of the hydrogen atom over that of its nucleus, or the power emitted in a supernova over that of an ordinary burning star, to name just two. Without a theory of nature, these large ratios may seem mystifying. With a theory of nature they follow from basic laws and the mystery disappears.
     
    Last edited: Apr 3, 2018
  20. Apr 3, 2018 #19

    ohwilleke

    User Avatar
    Gold Member

    It is worth noting that the beta function used by Shaposhnikov-Wetterich 09 is not the Standard Model beta function of the Higgs boson. It is modified to reflect the beta function that would exist in the Standard Model plus quantum gravity in the form of an asymptotic gravity massless spin-2 graviton that modifies the beta function of the Higgs boson from the Standard Model version. The asymptotic behavior of the tweaked Higgs boson beta function probably reflects this modification. So, the Shaposhnikov-Wetterich 09 beta function should not behave the same way that the different Higgs boson beta function modeled in Bednyakov et al 15 does.
     
  21. Apr 3, 2018 #20

    Urs Schreiber

    User Avatar
    Science Advisor
    Gold Member

    True, I was wondering about this. But Bednyakov et al. cite Shaposhnikov-Wetterich on their p, 17, right before they point out failure of asymptotically vanishing beta, as if in reply to that claim. But it's true, it's not clear (to me) whether they really operate on the same assumptions. Would be good to sort this out...
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Loading...
Similar Threads for Vacuum Metastability Date
I Quantum Vacuum Thursday at 6:22 PM
I Vacuum state of string theory Feb 7, 2018
A String vacua and particles? Nov 29, 2017
B Can the vacuum density produce only normal matter? Jun 22, 2017
Can the universe become stable with a new electroweak vacuum Jan 20, 2016