Quantum decoherence and the emergence of space/time and gravity

[shunyadragonvv]

TL;DR Summary

Quantum decoherence. and the emergence of continuous space/time and gravity

Does continuous space/time occur in Quantum smallest scale?

Quantum decoherence. and the emergence of continuous space/time and gravity

In another forum I have experienced a lot of combative dialogue asserting that continuous time/space is a property of the smallest Quantum scale. My present knowledge indicates this not true, and that the goal of the current research is determine how the properties of continuous time/space and gravity emerge from the Quantum smallest scale. I would like some feed back on this issue.

I realize this is a controversial subject as to how the emergence of time/space and gravity happen, but I did not believe that the concept of decoherence and that the large scale properties of continuous time/space were emergent properties of the Quantum smallest scale is controversial.

 

[PeterDonis]

We don't have a confirmed theory of quantum gravity, so we have no way of answering your question. All we have are various theoretical hypotheses that are being pursued with ongoing research.

 

[shunyadragonvv]

The question concerning Quantum Gravity is only part of topic. That would be simple based on the present evidence. Has gravity of the large scale been observed in Quantum particles? I fully realize the theoretical limits, and concerning this thread I am interested in the current knowledge of the concept of deconherence as to the nature of time at the Quantum smallest scale. Has any form continuous time of the large scale been observed as the smallest Quantum particle scale.

The

 

[PeterDonis]

Has gravity of the large scale been observed in Quantum particles?

No. Individual particles are many orders of magnitude too small for any gravitational effects from them to be observable.

Has any form continuous time of the large scale been observed as the smallest Quantum particle scale.

I don't know what you mean by this. We have seen no evidence of lack of continuity in spacetime at the smallest scales we can probe. Is that what you're asking?

 

[Grelbr42]

There have been some very preliminary experiments (preliminary but still quite interesting) on quantum particles in gravity fields. This is by no means getting anywhere close to gravity arising at quantum-level dimensions. So it is not an answer to the OP's questions in that regard. It only gets to quantum particles being individually affected by gravity.

Sadly, I don't have any links for either of these.

There have been some attempts to see if anti-particles fall at the same rate as particles. As far as I recall, the results were that they do, but the level of accuracy was very poor. This was a test that I remember from a seminar when I was in uni. They were dropping anti-protons. (Fermi lab? Not sure.) The issues were to get an experimental device that had weak enough electric and magnetic fields to let them drop a useful distance, and compare to regular protons. They had not entirely solved this, so the charged particles tended to get flung in unhelpful directions.

There have also been some experiments where a particle loses energy by rising through a gravity field, and so it has a very tiny little difference in energy that does interesting interferometry things. This was over-a-beer talk with a guy that was doing it for his PhD.

 

[PeterDonis]

There have been some attempts to see if anti-particles fall at the same rate as particles. As far as I recall, the results were that they do, but the level of accuracy was very poor.

Yes, experimental limitations at this time make it very difficult to get good accuracy for these experiments.

There have also been some experiments where a particle loses energy by rising through a gravity field, and so it has a very tiny little difference in energy that does interesting interferometry things.

The experiment I'm aware of along these lines was done with neutrons, and basically tests whether the Newtonian gravitational potential due to height acts the same way as any other potential in the non-relativistic Schrodinger Equation. The results indicate that it does, but this is just testing standard non-relativistic QM with a gravitational potential. It is not testing any quantum aspects of gravity itself.

 

[vanhees71]

There's at least one very accurate measurement on the behavior of neutrons in the gravitational field of the Earth, but for that the non-relativistic approximation is sufficient, and in this realm everything is as expected:

https://arxiv.org/abs/hep-ph/0306198
https://doi.org/10.1038/415297a

 

[Morbert]

Sean Carroll's recent-ish paper might be of some interest to OP

https://www.preposterousuniverse.com/blog/2016/07/18/space-emerging-from-quantum-mechanics/
https://arxiv.org/abs/1606.08444

 

[shunyadragonvv]

No. Individual particles are many orders of magnitude too small for any gravitational effects from them to be observable.I don't know what you mean by this. We have seen no evidence of lack of continuity in spacetime at the smallest scales we can probe. Is that what you're asking?

I agree. The subject relates to the problem of the mergence of time from entanglement of Quantum particles. I believe recent research supports this.

 

[shunyadragonvv]

Sean Carroll's recent-ish paper might be of some interest to OP

https://www.preposterousuniverse.com/blog/2016/07/18/space-emerging-from-quantum-mechanics/
https://arxiv.org/abs/1606.08444

Thank you for the reference!

 

[PeterDonis]

The subject relates to the problem of the mergence of time from entanglement of Quantum particles. I believe recent research supports this.

What research are you talking about? Do you have any references?

 

[vanhees71]

Quantum (Field) Theory as we know it and how particles are described is strongly based on a given spacetime structure, both in non-relativistic QM and special-relativistic QFT. The latter methods can be generalized to some extent to quantum field theory in "curved spacetime", i.e., in a given (classical) general-relativistic spacetime manifold. The quantization of the spacetime model itself so far has not been successful.

 

[shunyadragonvv]

Answer to a formula and relevance to emerging time.

Formula attached

 

[PeterDonis]

Answer to a formula and relevance to emerging time.

Formula attached

Formulas in attachments are not allowed. Please use the PF LaTeX feature to enter formulas directly in your post. There is a "LaTeX Guide" link at the lower left below each post window.

 

[shunyadragonvv]

I solved it myself

 

[PeterDonis]

I solved it myself

Solved what?

 

[shunyadragonvv]

The formula I could not post/

 

[PeterDonis]

The formula I could not post/

Are you going to post your solution?