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

[shunyadragon]

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 that the goal of the current research is determine how the emergent properties of continuous time/space emerge from the Quantum smallest scale/ I would like some feed back on this issue. Here is an interesting reference to start the dialogue.

I realize this is a controversial subject, 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.

Source: https://www.nature.com/articles/nphys3366

Universal decoherence due to gravitational time dilation

• Igor Pikovski,
• Magdalena Zych,
• Fabio Costa &
• Časlav Brukner

Nature Physics volume 11, pages668–672 (2015)Cite this articleAbstract


The physics of low-energy quantum systems is usually studied without explicit consideration of the background spacetime. Phenomena inherent to quantum theory in curved spacetime, such as Hawking radiation, are typically assumed to be relevant only for extreme physical conditions: at high energies and in strong gravitational fields. Here we consider low-energy quantum mechanics in the presence of gravitational time dilation and show that the latter leads to the decoherence of quantum superpositions. Time dilation induces a universal coupling between the internal degrees of freedom and the centre of mass of a composite particle. The resulting correlations lead to decoherence in the particle position, even without any external environment. We also show that the weak time dilation on Earth is already sufficient to affect micrometre-scale objects. Gravity can therefore account for the emergence of classicality and this effect could in principle be tested in future matter-wave experiments.

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Access to this article is limited. I will present another article maybe to the conrrary next.

[TheLurch]

I'm not sure I understand what your argument is. By "the smallest quantum scale", are you talking about the Planck length? And how do you contend that something continuous emerges from something with discrete units like that?

[shunyadragon]

I'm not sure I understand what your argument is. By "the smallest quantum scale", are you talking about the Planck length? And how do you contend that something continuous emerges from something with discrete units like that?

That is one of major focus of research at present, but we do not need to deal with it concerning my original questions. Does the Quantum smallest scale, which consists of Quantum particles have the properties of continuous time/space? I believe gravity cannot exist without continuous time/space. Gravity as we know exists in the macro world does not exist in the world of Quantum particles.

The emergence of continuous time/space and gravity from the Quantum scale is basically this is the process that took place in the expansion of the universe, if this is what happened(?). This is question of how Universal Decoherence and the emergence of tie/space and gravity takes place is unresolved though some claim to have the answer. It is accepted that the properties of our universe, ie time, space, and gravity are emergent properties of Quantum particles.

I may provie articles on the controvercy of how universal decoherence takes place.

[TheLurch]

That is one of major focus of research at present, but we do not need to deal with it concerning my original questions. Does the Quantum smallest scale, which consists of Quantum particles have the properties of continuous time/space?

You can't answer this without defining what the quantum smallest scale is. That's why I asked about the Planck length. That is, at least in quantum theory, where the continuity of spacetime should break down. But it's also far below any distance we can measure, so there's no way of knowing at the moment whether anything in particular happens at that length scale.

I believe gravity cannot exist without continuous time/space. Gravity as we know exists in the macro world does not exist in the world of Quantum particles.

And this statement is false. Gravity is described by relativity, and we see relativistic effects influencing quantum particles all the time. To give one obvious example, atomics clocks rely on quantum effects to operate, and we can use them to track the relativistic effects on time due to stronger gravitational fields:
https://www.nist.gov/news-events/new...r%20to%20Earth.

[shunyadragon]

And this statement is false. Gravity is described by relativity, and we see relativistic effects influencing quantum particles all the time. To give one obvious example, atomics clocks rely on quantum effects to operate, and we can use them to track the relativistic effects on time due to stronger gravitational fields:
https://www.nist.gov/news-events/new...r%20to%20Earth.

Yes. I agree gravity is described by Relativity, but the problem is in bold:

Source: https://plato.stanford.edu/entries/quantum-gravity/

Quantum Gravity, broadly construed, is a physical theory (still ‘under construction’) incorporating both the principles of general relativity and quantum theory. Such a theory is expected to be able to provide a satisfactory description of the microstructure of spacetime at the so-called Planck scale, at which all fundamental constants of the ingredient theories, c (the velocity of light in vacuo), ℏ (the reduced Planck’s constant), and G (Newton’s constant), come together to form units of mass, length, and time. This scale is so remote from current experimental capabilities that the empirical testing of quantum gravity proposals along standard lines is rendered near-impossible.

In most, though not all, theories of quantum gravity, the gravitational field itself is also quantized. Since the contemporary theory of gravity, general relativity, describes gravitation as the curvature of spacetime by matter and energy, a quantization of gravity seemingly implies some sort of quantization of spacetime geometry: quantum spacetime. Insofar as all extant physical theories rely on a classical (non-quantum) spacetime background, this presents not only extreme technical difficulties, but also profound methodological and ontological challenges for the philosopher and the physicist. Though quantum gravity has been the subject of investigation by physicists for almost a century, philosophers have only just begun to investigate its philosophical implications.

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They are still looking for the graviton, I believe that time, space and entopic gravity may be emergent properties of Quantum. Note: 'I believe.' :

Source: https://en.wikipedia.org/wiki/Entropic_gravity#:~:text=Entropic%20gravity%2C%20also%20known%20as,and%20not%20a%20fundamental%20interaction.

Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic force—a force with macro-scale homogeneity but which is subject to quantum-level disorder—and not a fundamental interaction.

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Also, this is an interesting article that address 'emergent time, and space.'

Source: https://www.preposterousuniverse.com/blog/2016/07/18/space-emerging-from-quantum-mechanics/

Space Emerging from Quantum Mechanics

70 Comments / arxiv, Science
The other day I was amused to find a quote from Einstein, in 1936, about how hard it would be to quantize gravity: “like an attempt to breathe in empty space.” Eight decades later, I think we can still agree that it’s hard.

So here is a possibility worth considering: rather than quantizing gravity, maybe we should try to gravitize quantum mechanics. Or, more accurately but less evocatively, “find gravity inside quantum mechanics.” Rather than starting with some essentially classical view of gravity and “quantizing” it, we might imagine starting with a quantum view of reality from the start, and find the ordinary three-dimensional space in which we live somehow emerging from quantum information. That’s the project that ChunJun (Charles) Cao, Spyridon (Spiros) Michalakis, and I take a few tentative steps toward in a new paper.

We human beings, even those who have been studying quantum mechanics for a long time, still think in terms of a classical concepts. Positions, momenta, particles, fields, space itself. Quantum mechanics tells a different story. The quantum state of the universe is not a collection of things distributed through space, but something called a wave function. The wave function gives us a way of calculating the outcomes of measurements: whenever we measure an observable quantity like the position or momentum or spin of a particle, the wave function has a value for every possible outcome, and the probability of obtaining that outcome is given by the wave function squared. Indeed, that’s typically how we construct wave functions in practice. Start with some classical-sounding notion like “the position of a particle” or “the amplitude of a field,” and to each possible value we attach a complex number. That complex number, squared, gives us the probability of observing the system with that observed value.

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Read on . . .