Is There a Possibility of Quantum Events Creating Cats?

[clarkvangilder]

Things don't "pop into existence" except in certain very special cases called transitions. And these have to obey certain rules such as conservation of energy, momentum, angular momentum, charge and a host of other quantum numbers. Whatever then "pops into existence" is accompanied by an appropriate change in the quantum numbers of whatever else is left behind in order to obey those conservation rules. Examples are radio-active decay and particle collisions. Even chemical reactions fall into this category. Cats (kittens) "pop into existence" through a complex chain of chemical reactions called conception and birth with conservation rules applying at every link in the chain.

Yes! This seems to me to be closer to the truth about the chances of obtaining a cat from the quantum _____________. There seems to be NO doubt that ALL of the particles needed can come from the quantum ___________; however, a complex macroscopic structure like a cat comes about through a longer and more complicated series of thermal fluctuations that would be understood classically.

BTW ... I am using "the quantum ____________" as a placeholder for what I do not understand. In NO way am I wanting to promote the fluctuation myth that has been so eloquently debunked in another discussion in the PF.

Also, I DO NOT dispute that when it comes down to it, we simply DO NOT, as Bill said, know.

 

[StandardsGuy]

Vacuum fluctuations aren't what you're thinking they are and they don't do what you're thinking they do. You might give this Insights article a try: https://www.physicsforums.com/insights/vacuum-fluctuation-myth/

So I take it that you don't think the universe came about from a quantum fluctuation. I was led to believe that this was a popular belief, though not one of mine.

 

[bhobba]

So I take it that you don't think the universe came about from a quantum fluctuation.

Its exactly as he said.

The theory you are thinking of is tunneling in the false vacuum:
https://en.wikipedia.org/wiki/False_vacuum

It is often said to be caused by quantum fluctuations but that is just loose terminology often found in popularization's and even otherwise good articles like the above.

Thanks
Bill

 

[StandardsGuy]

Its exactly as he said.

The theory you are thinking of is tunneling in the false vacuum:
https://en.wikipedia.org/wiki/False_vacuum

It is often said to be caused by quantum fluctuations but that is just loose terminology often found in popularization's and even otherwise good articles like the above.

Thanks
Bill

I was looking for clarification on what he said. Your link talks about the universe disappearing, not coming into existence. So I take it that YOU think it is more likely that the universe will disappear than a cat will pop into existence. Am I correct?

 

[bhobba]

I was looking for clarification on what he said. Your link talks about the universe disappearing, not coming into existence. So I take it that YOU think it is more likely that the universe will disappear than a cat will pop into existence. Am I correct?

From the link:
Expansion of bubble
Any increase in size of the bubble will decrease its potential energy, as the energy of the wall increases as the surface area of a sphere {\displaystyle 4\pi r^{2}} but the negative contribution of the interior increases more quickly, as the volume of a sphere {\displaystyle \textstyle {\frac {4}{3}}\pi r^{3}}Therefore, after the bubble is nucleated, it quickly begins expanding at very nearly the speed of light. The excess energy contributes to the very large kinetic energy of the walls. If two bubbles are nucleated and they eventually collide, it is thought that particle production would occur where the walls collide. The tunnelling rate is increased by increasing the energy difference between the two vacua and decreased by increasing the height or width of the barrier.

It doesn't explicicitly state this is how the universe was born the following makes it explicit:
https://ned.ipac.caltech.edu/level5/Guth/Guth3.html

'Once a patch of the early Universe is in the false vacuum state, the repulsive gravitational effect drives the patch into an inflationary period of exponential expansion. To produce a universe with the special features of the Big Bang discussed above, the expansion factor must be at least about 1025. There is no upper limit to the amount of expansion. Eventually the false vacuum decays, and the energy that had been locked in it is released. This energy produces a hot, uniform, soup of particles, which is exactly the assumed starting point of the traditional Big Bang theory. At this point the inflationary theory joins onto the older theory, maintaining all the successes for which the Big Bang theory is believed.'

It is how the big bang started and the mechanism of the so called 'universe from a fluctuation'. It leads more naturally to continuing inflation type theories where universes are being born all the time.

The point is while loose terminology like quantum fluctuation is used its really well known quantum tunneling type effects.

Thanks
Bill

 

[StandardsGuy]

From the link:
Expansion of bubble
Any increase in size of the bubble will decrease its potential energy, as the energy of the wall increases as the surface area of a sphere {\displaystyle 4\pi r^{2}} but the negative contribution of the interior increases more quickly, as the volume of a sphere {\displaystyle \textstyle {\frac {4}{3}}\pi r^{3}}Therefore, after the bubble is nucleated, it quickly begins expanding at very nearly the speed of light. The excess energy contributes to the very large kinetic energy of the walls. If two bubbles are nucleated and they eventually collide, it is thought that particle production would occur where the walls collide. The tunnelling rate is increased by increasing the energy difference between the two vacua and decreased by increasing the height or width of the barrier.

It doesn't explicicitly state this is how the universe was born the following makes it explicit:
https://ned.ipac.caltech.edu/level5/Guth/Guth3.html

'Once a patch of the early Universe is in the false vacuum state, the repulsive gravitational effect drives the patch into an inflationary period of exponential expansion. To produce a universe with the special features of the Big Bang discussed above, the expansion factor must be at least about 1025. There is no upper limit to the amount of expansion. Eventually the false vacuum decays, and the energy that had been locked in it is released. This energy produces a hot, uniform, soup of particles, which is exactly the assumed starting point of the traditional Big Bang theory. At this point the inflationary theory joins onto the older theory, maintaining all the successes for which the Big Bang theory is believed.'

It is how the big bang started and the mechanism of the so called 'universe from a fluctuation'. It leads more naturally to continuing inflation type theories where universes are being born all the time.

The point is while loose terminology like quantum fluctuation is used its really well known quantum tunneling type effects.

Thanks
Bill

Thanks, Bill. I didn't read that far. I read:

"In a 2005 paper published in Nature, as part of their investigation into global catastrophic risks, MIT physicist Max Tegmark and Oxford philosopher Nick Bostrom calculate the natural risks of the destruction of the Earth at less than 1 per giga year from all events, including a transition to a lower vacuum state. They argue that due to observer selection effects, we might underestimate the chances of being destroyed by vacuum decay because any information about this event would reach us only at the instant when we too were destroyed...
If measurements of these particles suggests that our universe lies within a false vacuum of this kind, then it would imply—more than likely in many billions of years[16][Note 1]—that it could cease to exist as we know it, if a true vacuum happened to nucleate.[16]"

So the universe would cease to exist as we know it. 'Disappeared' may not have been good terminology on my part. I'm less concerned about loose terminology than on the assumptions that people spit off as fact. An example would be the first sentence in your quote about repulsive gravity. It may be so, but it's not so just because a person with a phd proposed it. People want citations, but how good are they?

As you pointed out, it takes an initial vacuum before the tunneling can occur. Logically, that would have to have been in a prior universe, since there wasn't any vacuum here until it was created by the Big Bang. That prior universe would have its own time, so there WAS something before time in this universe. Would you be open to a Feynman Cat (a cat going backwards in time)? (Joking) Maybe a false cat?

Another quote from your link:
"In general, gravitation makes the probability of vacuum decay smaller; in the extreme case of very small energy-density difference, it can even stabilize the false vacuum, preventing vacuum decay altogether. We believe we understand this. For the vacuum to decay, it must be possible to build a bubble of total energy zero. In the absence of gravitation, this is no problem, no matter how small the energy-density difference; all one has to do is make the bubble big enough, and the volume/surface ratio will do the job..."

 

[bhobba]

Would you be open to a Feynman Cat (a cat going backwards in time)? (Joking) Maybe a false cat?

No. Particles or cats do not go backwards in time.

This idea of positrons being electrons going back in time is obvious nonsense as can be seen by the argument being reversible - an electron is a positron going backwards in time. Its another of those heuristic falsehoods the bedevil QFT.

And yes there was something before time in most modern cosmological theories - if before is appropriate without time. That's why when I hear this something from nothing nonsense then some philosophical mumbo jumbo either for or against it I sort of go - sigh. I remember one guy who constantly harped on you can't get something from nothing - its impossible and obviously so. I had to carefully explain modern theories but also just because in everyday life we don't see something from nothing it doesn't mean its not possible. He never got it.

Thanks
Bill