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Primordial black holes refute Higgs vacuum decay?

  1. Jul 21, 2015 #1
    http://arxiv.org/abs/1507.05760
    Higgs boson cosmology
    Ian G. Moss
    (Submitted on 21 Jul 2015)
    The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics from the electroweak phase transition one nanosecond after the big bang, on to the end of the present-day universe through vacuum decay. Higgs physics is wide-ranging, and gives an impetus to go beyond the Standard Models of particle physics and cosmology to explore the physics of ultra-high energies and quantum gravity.



    This is an interesting review of topics like Higgs inflation and the effects of the electroweak phase transition. But what's really news to me is the claim on page 12 that "the metastable Higgs vacuum is inconsistent with the existence of even a single primordial black [hole of mass 10^12 Kg] in our observable universe".

    The fact that the Higgs mass and the top mass place the standard model Higgs vacuum on the edge of metastability may be THE biggest clue about BSM physics that the LHC has given us. The reason for this near-metastability remains completely unknown, and there is also disagreement as to whether the vacuum is metastable (i.e. whether we are living in a false vacuum that will decay one day), or just close to the edge, but nonetheless stable.

    If metastability of the vacuum is in radical tension with the expected formation of primordial black holes, that's a very big hint about how not to interpret this clue. But how clear-cut is the contradiction?
     
    Last edited: Jul 22, 2015
  2. jcsd
  3. Jul 26, 2015 #2
    I am not a cosmologist; this is explaining my stupid question: "Do we have actually observed primordial black holes?" I suppose that the answer is "yes" because if it would be "no" then the incompatibility between a metastable vacuum and such holes would be meaningless.

    "Is it so strange to think that the vacuum is metastable since we know that it is expanding?" ( <=> If it would be stable, then nothing new would hapen in our universe!)
     
  4. Jul 26, 2015 #3

    mfb

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    No - at least not conclusively (they don't have signs "I am primordial"). Some models predict them, however.

    No idea about the validity of the approach in the arXiv reference.
     
  5. Aug 3, 2015 #4
    "Stability and UV completion of the Standard Model". An attack on the significance of the criticality or near-metastability of the SM. The argument is that even simple new physics at very high energies, has a much greater effect on whether the EW vacuum is stable, than small changes to the supposedly critical values of Higgs mass and top mass. This is demonstrated concretely with a very simple BSM theory.

    My interpretation is that the argument in this paper needs to be understood and in some way overcome - rebutted, shown to be a special case, etc - because it seems very unlikely that e.g. Shaposhnikov and Wetterich were able to predict the Higgs mass correctly, just through sheer luck. So I would still maintain that the criticality is real and significant. The skeptical argument in this paper might even be, in an ironic way, another clue to its correct interpretation.
     
  6. Aug 3, 2015 #5

    mfb

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    This is just cherry-picking. List of Higgs mass predictions - every mass in the range between LEP and Tevatron exclusion limits would have fitted to several predictions.
     
  7. Aug 4, 2015 #6

    ohwilleke

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    "No - at least not conclusively (they don't have signs "I am primordial")."

    They come pretty damn close. Operationally, they are defined as black holes with a mass of less than the minimum mass necessary to form a black hole through the gravitational collapse of a star which is somewhere in the vicinity of 2.5 to 3.2 solar masses (to one significant digit, 3 solar masses). Any smaller and it would have to have been formed by some other means that was available in the early universe but is no longer available today (hence the "primordial" name).

    If you see something that acts in all respects like a black hole with one solar mass, or for that matter, one lunar mass (each of which is entirely consistent with GR and entirely inconsistent with observation), you have a primordial black hole.

    So, false positives are not a problem. The trouble is false negatives. A primordial black hole can absolutely get bigger over time by gobbling things up, and any primordial black hole in existence today will have had 13.5 billion or so years to do just that. So, if you see a 3.5 solar mass small black hole in the middle of a dark filament or a galaxy cluster, for example, where there are no obvious impediments to black hole accretion (which may even be measurable directly at a rate that would put it under 2.5 solar masses about 13 billion years ago) and there is circumstantial evidence to expect that it is old, you might have a primordial black hole that just looks like a regular black hole.

    Then again, the notion that primordial black holes were observable and distinguishable once up a time but all look indistinguishable from ordinary black holes in the current era sounds a bit suspicious.

    At a sufficiently small size and in the right conditions, in principle, loss of mass from Hawking radiation should exceed gain of mass through stuff falling into it. But, that condition doesn't kick in anywhere near the primordial v. ordinary cutoff.
     
    Last edited: Aug 5, 2015
  8. Aug 5, 2015 #7

    mfb

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    A primordial black hole with a mass of 10 solar masses would not be called primordial? That's the mass region where we are missing the sign, and the reason for my description: some of the black holes we see could be primordial, but we have no way to know because all known black holes are massive enough to be stellar remnants.

    Small black holes could be so extremely rare and hard to see that we just didn't find them yet. At least I cannot rule it out.
     
  9. Aug 5, 2015 #8

    ohwilleke

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    You are right that a black hole with a mass of 10 solar masses could be primordial, but I very much doubt that anyone would interpret the finding in that way without some really solid indications that it had grown to the mass from less than the stellar black hole cutoff without some very strong circumstantial evidence.
     
  10. Aug 6, 2015 #9

    mfb

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    Exactly, that was my point with "they don't have a sign attached".
     
  11. Nov 15, 2016 #10
    "The Fate of the Higgs Vacuum", a quick review of this work. They have a calculation according to which, if the Higgs vacuum is metastable, a black hole of 100,000 Planck masses (or less) will almost instantly produce vacuum decay.
     
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