Vacuum Metastability: Estimating the Lifespan of a False Vacuum”

  • Context: Graduate 
  • Thread starter Thread starter physics9c
  • Start date Start date
  • Tags Tags
    Vacuum
Click For Summary

Discussion Overview

The discussion revolves around the concept of vacuum metastability and the implications of the universe potentially being in a false vacuum state. Participants explore the relationship between cosmic inflation and false vacuum scenarios, as well as attempts to estimate the lifespan of such a vacuum state.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question whether the acceleration of inflation implies that we exist in a false vacuum, noting the difficulty in finding definitive answers.
  • There are concerns about the reliability of estimates regarding the lifespan of a false vacuum, with some suggesting that a decay time of at least a Hubble time is not reassuring.
  • One participant expresses skepticism about the origin of the Hubble time estimate and seeks clarification on its basis.
  • Participants mention various academic papers that discuss vacuum decay and false vacua, but access to these papers is a barrier for some.
  • There is a discussion about the uncertainty surrounding the potential energy function of the field and its implications for calculating transition rates to a true vacuum.
  • Some participants express doubt about the existence of reliable models to predict the likelihood of vacuum decay events, citing the need for unknown constants in nature.
  • One participant references a specific probability of 1 in 169 billion for vacuum decay, questioning the validity of such estimates without a solid model.
  • There is a divergence of views on whether we can assert that we are in a false vacuum due to accelerating inflation, with some arguing that insufficient knowledge exists to make such claims.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus on the implications of cosmic inflation for false vacuum existence or the reliability of lifespan estimates. The discussion remains unresolved regarding the likelihood of vacuum decay and the validity of various models.

Contextual Notes

Participants highlight limitations in current understanding, including the dependence on unknown constants and the lack of a definitive model for vacuum decay. The discussion also reflects varying interpretations of existing literature and estimates.

physics9c
Messages
7
Reaction score
0
I recently learned about the possibility of the universe being in a false vacuum, but it seems really hard to find real information on it. I've looked at academic papers but they're well above my undergrad math.

Does the acceleration of inflation imply that we do exist in a false vacuum?

and if we are in a false vacuum, what are some reasonable estimates for its lifespan?

everywhere i look people seem to say "at least 13billion years" which doesn't seem to be saying much at all.


the thing is I can't find even tentative calculations on how long the universe would be expected to last even IF assumptions are given - like a higgs boson of 115Gev or something.

that makes the vacuum metastable, but why can't we calculate a half life from that?
 
Space news on Phys.org
i appreciate the article, as its one i actually haven't seen yet - and I've looked at about 100.

ill read it more in depth in a bit here but one sore point with me is that it reiterates a point that i don't find reassuring:

"the decay time is at least a Hubble time."

its like discovering a bomb was put in a building on monday, finding it on tuesday and saying - we can at least be assured that the bomb takes at least a day to explode. it says nothing about the future of what the bomb will do.

i like the bit about a rolling vacuum - if i understand it at all which of course i dont. that seems to suggest things are less likely to tunnel out in a bang and more likely to slowly fall into a new vacuum state?
 
physics9c said:
"the decay time is at least a Hubble time."
I don't know where that number came from either - always wondered about it. Maybe somebody else can explain.
 
Lawrence Krauss has a paper you may find interesting:

http://arxiv.org/abs/0711.1821
The Late Time Behavior of False Vacuum Decay: Possible Implications for Cosmology and Metastable Inflating States
 
it doesn't seem to give any good news though.

"If our universe is metastable, the expected survival time
may be not much larger than the current Hubble age."

all the rest is referred to as a "modicum of hope"
 
This is one of those things that we literally can't know. Given the potential energy function of the field providing the energy density, one can calculate transition rates to the true vacuum. But this function might not exist, and if it does, there's very little guidance from fundamental theory as to its probable form. If I were you, I'd be more nervous about an impending ekpyrotic brane collision wiping out the universe. That or a GRB frying the atmosphere ;)
 
i understand that academic journals need subscriptions to keep alive, but some of those articles are old. have any been released to the public yet?

i can't actually view any of them.

thanks though.
 
  • #10
physics9c said:
i can't actually view any of them.
Yeah, that's frustrating. You can always try google scholar; you can get the Coleman & De Luccia paper. In case you don't know of it, the arXiv eprint server has most recent stuff (from the 90's or so onwards) for free: "arxiv.org"[/URL]
Bousso's cosmological constant paper isn't available for free, but his TASI lectures on the same subject are available and probably similar in scope:
[PLAIN]http://arxiv.org/abs/0708.4231" .
 
Last edited by a moderator:
  • #11
i still can't seem to gather how likely the event is or even what the regional probabilities are.

i suppose it depends on unknown constants in nature but arent there conjectures based on existing models?

like.. if we assume higgs boson of 115Gev then... a probability of so many years.. etc.?
 
  • #12
I've actually been looking into the metastability event myself, but I don't think anyone could truly know. Any experimental evidence to suggest it exists would end the universe in the blink of an eye =P
 
  • #13
Does the acceleration of inflation imply that we do exist in a false vacuum?

Right now we are still trying to nail down the observations, and it's a bit premature to guess what might be causing the acceleration.

physics9c said:
i still can't seem to gather how likely the event is or even what the regional probabilities are.

At some point you get into the realm of philosophy. How do you define the likelihood of an event for which there is no good model for that event? At some point, you just have to say that you can't.

i suppose it depends on unknown constants in nature but arent there conjectures based on existing models?

Not really. Right now the fact that we are here constrains the theory more than the theory constrains the observations. The thing that makes it unlikely that the universe will go poof tomorrow is the fact that it's been around for 13 billion years.
 
  • #14
well I've seen in a nature article for example, a quote that said the chances are 1 in 169billion. it seems like that scientist involved must at least have had a model.

after all, there are models for quantum tunneling in other circumstances.

however, now i think the point is moot for another reason.

my understanding is that we almost certainly _are_ in a false vacuum because of accelerating inflation. given that, scientists have written articles about the possibility of triggering vacuum decay in a controlled environment - possibly in an attempt to gain energy - I am not sure why exactly.

in all the universe some civilization somewhere must eventually achieve this and there either will eventually be a mistake, or a religious zealot of some sort - I am sure all civilizations would have them - would detonate the device as an act of supreme faith in god.

which makes me think that it will in fact happen and might have already happened.
 
  • #15
physics9c said:
well I've seen in a nature article for example, a quote that said the chances are 1 in 169billion. it seems like that scientist involved must at least have had a model.

I'd be interested in seeing that article. I suppose you can argue that the chances are X given a certain model, but the big unknown is whether the model is correct or not.

my understanding is that we almost certainly _are_ in a false vacuum because of accelerating inflation.

That's not my understanding. We don't know nearly enough about cosmic acceleration or inflation to make that statement.
 
  • #16
Popular Science, February 2002,
"Hey, Who Switched Off The Universe"?
 

Similar threads

Undergrad Could cosmic rays induce a vacuum decay in the future?
  • · Replies 5 ·
Replies
5
Views
4K
Graduate Quantum fluctuations of the metastable false vacuum
  • · Replies 37 ·
2
Replies
37
Views
7K
Graduate What Does Prof Krauss Mean About False Vacuum Decay and Cosmology?
  • · Replies 8 ·
Replies
8
Views
2K
Graduate Vacuum Transitions and Lorentz Symmetry Breaking
  • · Replies 8 ·
Replies
8
Views
3K
Undergrad Questions about Negative Pressure and Vacuum Energy
  • · Replies 5 ·
Replies
5
Views
3K
High School What is the true vacuum and does it exist in our expanding universe?
  • · Replies 32 ·
2
Replies
32
Views
6K
Undergrad Is the false vacuum theory not well accepted?
  • · Replies 1 ·
Replies
1
Views
2K
High School Estimates — True Size of the Universe?
  • · Replies 33 ·
2
Replies
33
Views
8K
High School True/False Vacuum, Metastability & Stephen Hawking's Higgs Boson
  • · Replies 1 ·
Replies
1
Views
2K
Graduate Do cosmologists take spontaneous symmetry breaking seriously?
  • · Replies 34 ·
2
Replies
34
Views
5K