I Is Vacuum Decay from a False to True State Impossible or Just Unlikely?

AI Thread Summary
The discussion centers on the possibility of vacuum decay from a false vacuum to a true vacuum state, referencing a paper that argues against such decay occurring in certain quantum gravity models. It suggests that if decay were to happen, it would transition into an open FRW spacetime with zero cosmological constant rather than a flat or Anti-de Sitter spacetime. Additionally, a CERN physicist proposed that a true vacuum could be excited into a false vacuum by injecting energy, though no specific sources were provided to support this claim. Participants are seeking further literature to substantiate these ideas. The conversation highlights ongoing debates in theoretical physics regarding vacuum states and their transitions.
Suekdccia
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I vacuum decay impossible
I found this paper (https://arxiv.org/pdf/hep-th/0211160.pdf) which argues against the possibility of a decay from a metastable vacuum to a true vacuum state. However, this is the first time I've read this. Is it then impossible that a vacuum decay from a false vacuum may occur (even in principle)? Or is it just unlikely (but not strictly impossible)?

Also, I've been told in an email by CERN physicist Gian Carlo Giudice that a true vacuum state could be excited into a false one by "injecting" energy to the vacuum (like with high-energy cosmic rays). However, he did not give any specific source, although what he said seems perfectly logical (if there was energy present in the true vacuum state, why couldn't it excited into a metastable state?) Could you give me some?
 
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Suekdccia said:
argues against the possibility of a decay from a metastable vacuum to a true vacuum state
Not really, no. It argues that, in a certain kind of quantum gravity model, if you start with de Sitter spacetime (i.e., a positive cosmological constant), and such a decay occurs, it will not be into a flat or Anti-de Sitter (AdS--negative cosmological constant) spacetime, but into an open FRW spacetime with zero cosmological constant.
 
PeterDonis said:
Not really, no. It argues that, in a certain kind of quantum gravity model, if you start with de Sitter spacetime (i.e., a positive cosmological constant), and such a decay occurs, it will not be into a flat or Anti-de Sitter (AdS--negative cosmological constant) spacetime, but into an open FRW spacetime with zero cosmological constant.
Thank you

Also, I've been told in an email by CERN physicist Gian Carlo Giudice that a true vacuum state could be excited into a false one by "injecting" energy to the vacuum (like with high-energy cosmic rays). However, he did not give any specific source, although what he said seems perfectly logical (if there was energy present in the true vacuum state, why couldn't it excited into a metastable state?) I haven't been able to find any clear sources about this. Are any of these such papers?

https://arxiv.org/abs/1104.1305 see ref.14 in page 2

https://arxiv.org/abs/gr-qc/9905093

https://arxiv.org/abs/1108.0417

If not, do you have any?
 
https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?
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