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Vacuum metastability

  1. Jul 26, 2010 #1
    When the LHC was starting up, there were some worries that a collision of two particles could form a bubble of "true vacuum", as opposed to the "metastable vacuum" that the universe is in today. This bubble would then expand outward at the speed of light, annihilating any matter that stood in its way.

    Studies later found that cosmic ray collisions, both past and present, took place at energies much higher than those that human-made collisions are capable of, which meant that the LHC is safe.

    However, sooner or later, humans will be able to create collisions that are as powerful as, and eventually more powerful than, naturally occurring collisions. Could one of those collisions set off what's known as the vacuum metastability disaster? In other words, could it be that there's a certain energy barrier that naturally-occurring collisions can't overcome but that human-made collisions could overcome? After all, it's not that far-fetched to think that humanity can create collisions that are more energetic than natural collisions. There are several things we can do better than nature.
  2. jcsd
  3. Jul 26, 2010 #2
    It wasn't "studies later found". The cosmic rays have been known for a long time.

    There was some interesting discussion on this between Marc Sher and Motl http://js-kit.com/api/static/pop_comments?ref=http%3A%2F%2Fmotls.blogspot.com%2F2010%2F07%2Fwhat-light-higgs-would-mean-for.html&title=The%20Reference%20Frame%3A%20What%20a%20light%20Higgs%20would%20mean%20for%20particle%20physics&path=%2F6003671096352302856&standalone=no&scoring=yes&backwards=no&sort=date&thread=yes&permalink=http%3A%2F%2Fjs-kit.com%2Fapi%2Fstatic%2Fpop_comments%3Fref%3Dhttp%253A%252F%252Fmotls.blogspot.com%252F2010%252F07%252Fwhat-light-higgs-would-mean-for.html%26path%3D%252F6003671096352302856&skin=echo&smiles=no&editable=yes&thread-title=Echo&popup-title=Echo&page-title=The%20Reference%20Frame%3A%20What%20a%20light%20Higgs%20would%20mean%20for%20particle%20physics" [Broken]. Apparently, cosmic rays hitting a static target may give a center-of-mass energy as low as 10^5 GeV, but even if they did have enough energy, the area affected may be too small to create a vacuum transition event. I haven't read the papers linked - they might be interesting.

    As I commented there, I'm not sure why one would assume the highest energy events found in nature would occur in the Earth's atmosphere. Apparently there's no real obvious place to find higher energies though.
    Last edited by a moderator: May 4, 2017
  4. Jul 26, 2010 #3
    Wasn't it a drop in the vacuum energy that caused the initial inflation? So wouldn't another drop in the vacuum energy be accompanied by another round of hyper-inflation?
  5. Jul 27, 2010 #4
    Collisions between cosmic rays and neutron stars are an excellent place to look. Neutron stars are very hot (100 MeV/nucleon when they are born), and they are so dense that you get a large number of events in compact space. If we haven't reverted to true vacuum in 15 GYr, given the number of neutron stars in our causal past ... that should set some limits on creation of true vacuum in high-energy collisions.

    Look on the bright side: you wouldn't even notice that anything happened. You'd just cease to exist.
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