Is There a Speed Limit for Spacetime Expansion in Quantum Field Theory?

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Discussion Overview

The discussion centers around the concept of spacetime expansion in the context of quantum field theory (QFT) and the implications of quantum mechanics (QM) on our understanding of reality. Participants explore the nature of particle creation, the significance of quantization, and the philosophical underpinnings of physical theories.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Meta-discussion

Main Points Raised

  • Some participants propose that the Feynman path integral formulation suggests that particles can have multiple possible paths and locations during their creation, raising questions about the nature of existence and non-existence.
  • Others argue that quantum field theory quantizes fields into discrete particles, such as photons, and that this quantization is essential for understanding physical phenomena.
  • A participant expresses a desire to understand why quantization is necessary, suggesting that the path integral formulation might indicate a deeper symmetry in nature that is broken in observable phenomena.
  • Another participant emphasizes the importance of considering symmetries at the level of the Hamiltonian or Lagrangian rather than focusing solely on amplitudes, noting the infinite number of paths involved in quantum mechanics.
  • Some participants challenge the notion that quantization can be understood purely through observable phenomena, arguing that deriving physics from first principles is crucial for a deeper understanding of reality.
  • There are claims that the discussion of deriving physics from principles rather than observations is seen as pseudo-science or philosophical gibberish by some participants.
  • One participant suggests that if the only certainty is the existence of the universe, then the nature of spacetime might be derived from considering all possible alternatives and configurations.

Areas of Agreement / Disagreement

Participants express a range of views on the necessity of quantization and the interpretation of quantum mechanics, with no clear consensus reached. Some defend the importance of observable phenomena, while others advocate for a more principle-based approach to understanding reality.

Contextual Notes

Limitations in the discussion include unresolved questions about the foundational principles of quantum mechanics and the implications of quantization, as well as differing interpretations of what constitutes a valid explanation in physics.

  • #31
selfAdjoint said:
LQG has its webs and foams, all connected, and digital physics cells are static. In both cases they are not the phenomenal spacetime which is a "limiting case" of their actions.
I'm not sure these work with a universe growing out of a singularity. If it does not grow from a singularity, then you have to contend with the illogic of instantaneous existence which by definition defies explanation and thus logic. If the universe did grow from a singularity, then at the differential level, spacetime (at least to begin with) must have a continuous structure in all directions (no webs or foams at this level). I would think think that if spacetime grew from a singularity, then all of spacetime from the beginning must inherit this feature of its roots. Otherwise, I think the change from such a continuous distribution to anything else would imply some very serious topology changes that probably cannot be explained.
 
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  • #32
Now I wonder if time must be connected and continuous, and space must be connected and continuous, then does this imply some maximum speed that spacetime can expand. For if it cannot expand instantaneously because instantaneous existence defies any reason for its existence and so would defy logic, then does the connectedness of space/time imply some speed limit to the expansion. This would probably be connected to the speed of light as well. Thoughts anyone?
 

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