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I've been told that very energetic cosmic rays could cause a vacuum phase transition or vacuum decay (and even could cause a true vacuum level to go "uphill" to a false vacuum) due to their high energy levels.

I've found some references supporting this claim 1, 2, 3, 4

But also one paper arguing that vacuum decay induced by particle collisions (such as cosmic rays collisions) would be suppressed and no amount of cosmic rays collisions occurring in nature (even in the largest production sites) could trigger such phenomenon 5. But at the same time, the author speculates that in the future with powerful colliders we could cause a vacuum decay. However, I don't really get how the author says that a futuristic civilization could get enough energy to cause a vacuum phase transition while saying that even the most energetic events in the universe producing high-energy cosmic rays (like quasars and AGN) would fail to do so. I mean, I'm pretty sure there will be more energy in such natural events than in a particle collider even if we are talking about futuristic potential scenarios.

Therefore, is it possible or not that cosmic rays collisions may trigger such a vacuum decay? And if not, or if it is unclear, could it be triggered by other mechanisms (like certain types of black holes for example)?

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    $\begingroup$ Isn't everything regarding vacuum decay speculative at best? Also, it seems you're basically asking us to read a 24 page document (at minimum) and regurgitate the information contained to provide you with an answer, which isn't really something we do here. $\endgroup$
    – Kyle Kanos
    Commented Jun 25 at 13:06
  • $\begingroup$ Though just by reading the abstract on the arxiv link, it looks like they're assuming that a futurist collider could focus the particle collisions and force the required threshold of Higgs quant required for the decay (and presumably the focusing isn't something that natural CR colliders can do). $\endgroup$
    – Kyle Kanos
    Commented Jun 25 at 13:11
  • $\begingroup$ If this were possible, then it would have been triggered a long time ago by other technical civilizations. Since it hasn't we can be sure that the authors of your source are wrong. $\endgroup$
    – FlatterMann
    Commented Jun 25 at 13:30
  • $\begingroup$ @FlatterMann perhaps the civilization that did this is outside our cosmological horizon :) $\endgroup$
    – vengaq
    Commented Jun 27 at 10:07
  • $\begingroup$ @vengaq That sets an extremely low limit on civilizations in the universe. I don't subscribe to such statements. They are, IMHO, a fallback to geocentrism and claims of special creation of the human race. Let's leave such nonsense for tribal politics. $\endgroup$
    – FlatterMann
    Commented Jun 27 at 12:19

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The usual line of reasoning about vacuum decay treats it as a random phenomenon: there are events where it might be triggered, and since it has not happened yet we get a bound on how likely it is. Normal physics papers do not assume civilizations as possible triggers, but it does not matter: a supercivilization is just a rare physical phenomenon too, not too different from a gamma ray burst except that we have not observed any so far. So you can bound the probability due to any kind of cause based on observing the current universe, getting a rate $\ll 10^{-9}$ per year (Tegmark & Bostrom 2005).

This is similar to many other arguments that came up about particle accelerator risks: if the LHC could trigger vacuum decay, strangelets, black holes or other bad things, we should expect to observe many such events due to cosmic rays. We don't, so we have a good reason to not to be worried. (Some complications and conditions apply, see (Ord, Hillerbrand & Sandberg 2008)).

One can argue that it takes a deliberate trigger to put nature into a state that is exceedingly improbable normally (after all, fusion triggered by fission chain reactions are very rare in nature but humans set them up). That is dealt with by the Tegmark & Bostrom argument for our past lightcone, but if you also think supercivilizations have a nonstationary emergence rate (not too crazy, perhaps) then past data does not give any assurances. Current physical theory on the other hand places few bounds on what clever minds wielding technologies we do not yet have can and cannot do, so it is hard to do a good assessment. But we have decent reasons to think natural causes have had a lot of gigalightyear hypervolumes to play out in, and so far they have not produced these effects due to black holes of all sizes, cosmic rays under extreme conditions, and other unusual conditions.

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  • $\begingroup$ plus LHC's blackhole isn't going to be at rest in the lab frame...it's going to zing off into space on a tangent to Geneva, evaporation notwithstanding. $\endgroup$
    – JEB
    Commented Jun 25 at 16:02
  • $\begingroup$ @JEB - That is one of the complications, since cosmic rays definitely do produce debris with above escape speed velocities due to momentum conservation, but it takes a fair bit of effort to show that LHC debris is likely to have it (after all, the system is supposed to have net zero momentum in the lab frame). $\endgroup$
    – Anders Sandberg
    Commented Jun 26 at 5:01
  • $\begingroup$ The thing is, would it be completely impossible that in natural sources the cosmic rays get sufficiently concentrated to trigger such a decay (as the paper from Strumia seems to suggest) @AndersSandberg $\endgroup$
    – vengaq
    Commented Jun 27 at 10:05
  • $\begingroup$ @vengaq - While the paper scenario looks extremely improbable, there is a lot of weird things in nature. While we can estimate plausibility of particular scenarios, it is usually good to also bound entire classes of scenarios we do not even know what they are, when estimating risk. $\endgroup$
    – Anders Sandberg
    Commented Jun 27 at 16:28

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