I Can there be quantum fluctuations without spacetime?

[Suekdccia]

TL;DR

Can quantum fluctuations occur without spacetime, giving a possible explanation for the origin of spacetime and the universe?

There is a paper called "On nothing" (https://arxiv.org/abs/1111.0301) which goes on to argue that the universe could not have arisen from a state without spacetime (as some proposals do using quantum fluctuations to explain how the universe was born without spacetime)

However, there is a recent article that refutes these arguments (https://arxiv.org/abs/2307.13614) in section 2.6

Is that correct? Has the paper been refuted? Can quantum fluctuations occur without spacetime, giving a possible explanation for the origin of spacetime and the universe?

 

[A. Neumaier]

The definition of a quantum fluctuation involves spacetime correlation functions. Thus without spacetime, these correlations and hence quantum fluctuations cannot even be defined.

 

[haushofer]

It all boils down to our understanding of spacetime at the quantum level. Which is imho, regardless of all those good intentions concerning strings and loops, still rather non-existent.

So the first question one should ask in this topic, is: according to which model or hypothesis?

 

[PeterDonis]

Moderator's note: Thread moved to the Beyond the Standard Models forum.

 

[PeterDonis]

Can quantum fluctuations occur without spacetime, giving a possible explanation for the origin of spacetime and the universe?

This question can't be answered since we do not have a theory of quantum gravity that has undergone any experimental tests, nor do we expect to be able to get one any time soon. Anything anyone says on this topic is speculative at this point.

 

[PeterDonis]

However, there is a recent article that refutes these arguments (https://arxiv.org/abs/2307.13614) in section 2.6

Section 2.6 does not "refute" those arguments, it agrees with them. Both papers define "nothing" as a limiting case of anti-de Sitter spacetime--i.e., as a spacetime, not as the absence of a spacetime.