tom.stoer said:What exactly do you mean by "collective"?
I would say that coherent states are - from the perspective of elementary excitations - something like collective modes.
I am not sure if the concept of collective excitations carries over to SF, because the foam does not "vibrate", it exists. And the existence of a huge macroscopic SF is already in some sense a collective excitation on the vacuum, just as a macrosocopic coherent state of photons.
So I would say that a semiclassical spacetime is a collective mode. Therefore your question is closely related to the question if semiclassical spacetime exists in SF models.
I have to check. There are papers regarding coherent states; I think these are rather close to semiclassical spacetime. In addition there are papers regarding the long-wavelength limit for the graviton propagator, again related to semiclassical spacetime.ensabah6 said:Do semiclassical spacetime exist in SF models?
tom.stoer said:I have to check. There are papers regarding coherent states; I think these are rather close to semiclassical spacetime. In addition there are papers regarding the long-wavelength limit for the graviton propagator, again related to semiclassical spacetime.
ensabah6 said:Can conventional SM QFT be easily coupled to SF models?
Collective modes in Spin Foams or Loop Quantum Gravity (LQG) refer to the collective behavior of the fundamental building blocks of space and time, known as spin networks. These collective modes describe how the spin networks interact and evolve over time, leading to the emergence of spacetime geometry.
Collective modes in Spin Foams or LQG are studied using mathematical tools, such as group field theory and spin foam models. These models allow scientists to simulate and analyze the behavior of spin networks and their collective modes, providing insight into the underlying structure of space and time.
The study of collective modes in Spin Foams or LQG is significant as it provides a deeper understanding of the fundamental structure of spacetime at the quantum level. It also has potential implications for theories of quantum gravity and could help bridge the gap between quantum mechanics and general relativity.
At present, there is no experimental evidence for the existence of collective modes in Spin Foams or LQG. However, scientists are working on developing experimental tests that could potentially verify the predictions of these theories and confirm the existence of collective modes.
Collective modes in Spin Foams or LQG are a unique aspect of these specific theories of quantum gravity. They are closely related to other concepts such as holography and entanglement, and provide a different perspective on how quantum gravity may manifest at the fundamental level.