The Nature of Spacetime:

[beecee]

My questions here were prompted by the following article.....

https://futurism.com/rethinking-space-time-nature/

 

extract: 

Quote

 In the 1970s, physicists Stephen Hawking and Jacob Bekenstein noted a link between the surface area of black holes and their microscopic quantum structure, which determines their entropy. This marked the first realization that a connection existed between Einstein’s theory of general relativity and quantum mechanics.

Quote

Less than three decades later, theoretical physicist Juan Maldacena observed another link between between gravity and the quantum world. That connection led to the creation of a model that proposes that spacetime can be created or destroyed by changing the amount of entanglement between different surface regions of an object.

In other words, this implies that spacetime itself, at least as it is defined in models, is a product of the entanglement between objects

Question: How valid is the first quote?

With regards to the second quote, here is the paper......

https://arxiv.org/pdf/1712.02803.pdf

Bulk Entanglement Gravity without a Boundary: Towards Finding Einstein’s Equation in Hilbert Space:

Abstract

We consider the emergence from quantum entanglement of spacetime geometry in a bulk region. For certain classes of quantum states in an appropriately factorized Hilbert space, a spatial geometry can be defined by associating areas along codimension-one surfaces with the entanglement entropy between either side. We show how Radon transforms can be used to convert this data into a spatial metric. Under a particular set of assumptions, the time evolution of such a state traces out a four-dimensional spacetime geometry, and we argue using a modified version of Jacobson’s “entanglement equilibrium” that the geometry should obey Einstein’s equation in the weak-field limit. We also discuss how entanglement equilibrium is related to a generalization of the RyuTakayanagi formula in more general settings, and how quantum error correction can help specify the emergence map between the full quantum-gravity Hilbert space and the semiclassical limit of quantum fields propagating on a classical spacetime.

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Quite a lengthy paper, which I would like comments on generally. In particular, is this a long sort after TOE? Or is this still along the same lines of string theory and its many derivatives? That is, mathematically beautiful  but we simply at this stage can never verify the validity of the proposal due to our lack of precision in being able to masure at such scales?

 

[Markus Hanke]

8 hours ago, beecee said:

Question: How valid is the first quote?

Well, it’s a valid conclusion, at least in the context of our current level of knowledge and understanding. We even have a model that can directly describe how this entropy comes about - loop quantum gravity. It is possible to do the maths via LQG, and obtain the Bekenstein-Hawking entropy equation. This is a very fascinating thing, because if we take LQG at face value, then we will be forced to completely rethink the nature of space and time. It would be a major paradigm shift.

8 hours ago, beecee said:

Quite a lengthy paper, which I would like comments on generally. In particular, is this a long sort after TOE?

No, because that model only describes the vacuum and gravity, but does not unify the other fundamental interactions.

8 hours ago, beecee said:

Or is this still along the same lines of string theory and its many derivatives?

No, String Theory assumes a smooth and continuous background spacetime from the beginning, so it doesn’t explain how such a spacetime comes about. It only explains how its geometry emerges, which isn’t quite the same thing. The approach in this paper on the other hand models an emergence of spacetime itself from more fundamental principles.

8 hours ago, beecee said:

but we simply at this stage can never verify the validity of the proposal due to our lack of precision in being able to masure at such scales?

Yes, at present it would be difficult to directly test such proposals. However, there may be ways to test it indirectly through observations - for example, just as there is a CMBR left over from the BB, there should also be a background of gravitational wave echos. It may (!) be possible that such a background provides clues as to the quantum structure of spacetime in the earliest moments of the universe.

[beecee]

13 hours ago, Markus Hanke said:

Well, it’s a valid conclusion, at least in the context of our current level of knowledge and understanding. We even have a model that can directly describe how this entropy comes about - loop quantum gravity. It is possible to do the maths via LQG, and obtain the Bekenstein-Hawking entropy equation. This is a very fascinating thing, because if we take LQG at face value, then we will be forced to completely rethink the nature of space and time. It would be a major paradigm shift.

No, because that model only describes the vacuum and gravity, but does not unify the other fundamental interactions.

No, String Theory assumes a smooth and continuous background spacetime from the beginning, so it doesn’t explain how such a spacetime comes about. It only explains how its geometry emerges, which isn’t quite the same thing. The approach in this paper on the other hand models an emergence of spacetime itself from more fundamental principles.

Yes, at present it would be difficult to directly test such proposals. However, there may be ways to test it indirectly through observations - for example, just as there is a CMBR left over from the BB, there should also be a background of gravitational wave echos. It may (!) be possible that such a background provides clues as to the quantum structure of spacetime in the earliest moments of the universe.

Near aligning to what I actually thought...just needed some professional confirmation....thanks.