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True Vacuum Questions

Anonymous Tue 09 Jun 00:19:34 2020 No.11776001 View Reply Original Report

Quoted By: >>11776085 >>11776139 >>11777032

I don't know much about true vacuums and how they behave, so I have couple hypothetical questions for the physicists on this board.

If a true vacuum occurred,

1. How much energy is actually produced and how does this energy interact with the universe?
2. And if the vacuum chain reaction is stopped at a certain point, would space as a false vacuum move back in to fill that truly empty area of the true vacuum or would it continue getting pushed outward by the energy that created the true vacuum in the first place?

Anonymous

Anonymous Tue 09 Jun 2020 00:40:56 No.11776085 Report

Quoted By: >>11776115 >>11776151

>>11776001
heisenberg uncertainty (which always occurs as far as we know) prevents any notion of a true vacuum of any significant size--there's always some low level noise. combined with our ideas of dark energy, there's also always a tiny positive pressure.
i think you'd need negative energy to make your vacuum, which only exists mathematically and would need entirely new physics to explain.

Anonymous

Anonymous Tue 09 Jun 2020 00:46:26 No.11776115 Report

Quoted By: >>11776146 >>11777539

>>11776085
Ah, okay. Would that have any relationship to the concept of white holes (which are also mathematically possible but seem to be physically impossible)?

Anonymous

Anonymous Tue 09 Jun 2020 00:53:14 No.11776139 Report

Quoted By:

>>11776001
The interior of the bubble has less energy density than the outside (that's what makes it the true vacuum). The walls of the bubble have more energy density than the outside (that barrier is what makes the outside metastable). Small bubbles might cost more energy on the surface then they make up in the interior, so they don't want to grow. Once you get past a critical size though it will keep growing.

Anonymous

Anonymous Tue 09 Jun 2020 00:54:13 No.11776146 Report

Quoted By: >>11777539

>>11776115
I don't know nearly enough math for it, but sure, you can acheive almost anything if you're allowed to invent new phenomena.

For instance, a black hole is a maximally dense region of space that more or less absorbs all energy at its surface boundary.
A white hole could be a maximally sparse region of space (true vacuum) which thus emits extreme energy at its boundary.

Anonymous

Anonymous Tue 09 Jun 2020 00:55:28 No.11776151 Report

Quoted By: >>11776177

>>11776085
You don't know what you are talking about. The notion of vacuum is always quantum mechanical. It's still a well defined lowest energy state.

Anonymous

Anonymous Tue 09 Jun 2020 01:01:49 No.11776177 Report

Quoted By: >>11778381

>>11776151
thats why i said "of any significant size"

Anonymous

Anonymous Tue 09 Jun 2020 05:34:39 No.11777032 Report

Quoted By: >>11777054 >>11778394

>>11776001
First of all, vacuums -- even "true" vacuums -- are not "empty" in a classical sense. We don't fully understand the interaction between QFT and GR, but absolute energy levels do not have meaning in a non-gravitational theory, and even the currently measured universal vacuum has a negative gravitational energy, evidenced by measure cosmological expansion.
A "true" vacuum is simply a vacuum with a lower energy than the current vacuum. When you say "empty" you probably think of a lack of particles, but in QFT the field is fundamental, not the particles. We define the number of particles _relative_ to the vacuum by counting the momenta for which the field is excited and the strengths of these excitations relative to the vacuum.
The popuþar example of a possible false vacuum is in the Higgs field. The Higgs potential is tachyonic, meaning the potential has a local maximum at the origin, so the symmetry is spontaneously broken as the field "rolls down" the potential to the nearest local minimum. This is typically modelled as a "Mexican hat" potential (looks like a sombrero) ~r^4-ar^2 for some positive a. The Higgs boson is the excitation that runs around the rim of the hat.
Some theorize that the potential has a second lower minimum further from the origin, separated from the first by a local maximum. The Higgs field would then be expected to tunnel to the lower minimum after a certain time depending on the exact shape of the potential under free conditions. The new minimum is the true vacuum. The Higgs boson energy would then differ, affecting the mass of force carriers of the strong force, possibly drastically affecting the stability of composite particles like neutrons and protons that make up atoms.

Anonymous

Anonymous Tue 09 Jun 2020 05:43:52 No.11777054 Report

Quoted By: >>11777061

>>11777032
>popuþar
how is it even possible to make a typo like this?

Anonymous

Anonymous Tue 09 Jun 2020 05:46:21 No.11777061 Report

Quoted By:

>>11777054
icelandic keyboard

Anonymous

Anonymous Tue 09 Jun 2020 09:56:24 No.11777539 Report

Quoted By:

>>11776115
>white holes
>>11776146
>black hole
>>>/x/

Anonymous

Anonymous Tue 09 Jun 2020 15:43:19 No.11778381 Report

Quoted By:

>>11776177
No, you were simply wrong. A vacuum is analogous to the ground state of a harmonic oscillator. Sure you can talk about quantum fluctuations in the ground state of a harmonic oscillator but it still is the very minimum energy level.

Your comments about dark energy, positive pressure, negative energy and all that are just completely off the mark. People that don't know any physics (like OP and like yourself) can't tell the difference between the things you are saying and the things I am saying. It just contributes to noise. It's why physics threads are so bad on this board.

Anonymous

Anonymous Tue 09 Jun 2020 15:47:03 No.11778394 Report

Quoted By:

>>11777032
>absolute energy levels do not have meaning in a non-gravitational theory
Sure but a minimum energy level absolutely has meaning. On the contrary it's when you start adding in gravity that a vacuum becomes more difficult to define.

>even the currently measured universal vacuum has a negative gravitational energy
Negative pressure not energy density

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