I Can there be quantum fluctuations without spacetime?

Suekdccia
Messages
352
Reaction score
30
TL;DR Summary
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?
 
Physics news on Phys.org
The definition of a quantum fluctuation involves spacetime correlation functions. Thus without spacetime, these correlations and hence quantum fluctuations cannot even be defined.
 
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?
 
Moderator's note: Thread moved to the Beyond the Standard Models forum.
 
Suekdccia said:
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.
 
Suekdccia said:
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.
 
https://arxiv.org/pdf/2503.09804 From the abstract: ... Our derivation uses both EE and the Newtonian approximation of EE in Part I, to describe semi-classically in Part II the advection of DM, created at the level of the universe, into galaxies and clusters thereof. This advection happens proportional with their own classically generated gravitational field g, due to self-interaction of the gravitational field. It is based on the universal formula ρD =λgg′2 for the densityρ D of DM...
Many of us have heard of "twistors", arguably Roger Penrose's biggest contribution to theoretical physics. Twistor space is a space which maps nonlocally onto physical space-time; in particular, lightlike structures in space-time, like null lines and light cones, become much more "local" in twistor space. For various reasons, Penrose thought that twistor space was possibly a more fundamental arena for theoretical physics than space-time, and for many years he and a hardy band of mostly...
Back
Top