I recently read an article by Yasunori Nomura (https://arxiv.org/abs/1711.05263), in which he says that space-time is an emerging phenomenon. At the same time, space-time disappears when the holographic degrees of freedom are maximally entangled and when there is no entanglement at all.

Do I understand correctly that one can say:

  1. Before the appearance of space-time, the universe was in a state in which the entanglement between the holographic degrees of freedom was zero.

  2. Can there be a situation in quantum mechanics in which the subsystems are absolutely not entangled and suddenly, spontaneously, begin to entangle?

  • $\begingroup$ If the Hamiltonian acting on the total system contains an interaction term, they will entangle on their own. E.g. the two electrons in a Helium atom are entangled in all of position, momentum, and spin. $\endgroup$ Dec 3 '20 at 18:29
  • $\begingroup$ @The_Sympathizer That is, they will be absolutely not entangled for some time, then suddenly they will get entangled? $\endgroup$ Dec 3 '20 at 18:32
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    $\begingroup$ I am not sure to understand, but to use that machinery the cosmological constant should be negative (AdS). Our universe has a positive constant. How should one fix this problem? $\endgroup$ Dec 3 '20 at 19:41
  • $\begingroup$ @ValterMoretti I don’t know why you say that ‘to use that machinery the cosmological constant must be negative’, can you please explain the premises of this claim. $\endgroup$ Dec 5 '20 at 7:27
  • $\begingroup$ @Wakabaloola By reading (quite superficially) the paper you quoted, I have had the impression that the thesis promoted in the work relies upon the assumption that the cosmological scenario is essentially an AdS spacetime (at least at space infinity, am I right?). Well, it is very very well known that our universe has a positive cosmological constant whereas AdS has a negative cosmological constant. How does our spacetime can be viewed as an emergent property of entangled states, if our spacetime is not the one assumed in the paper? $\endgroup$ Dec 5 '20 at 10:01

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