Discussion Overview
The discussion revolves around the existence of collective modes in Spin Foams (SF) and Loop Quantum Gravity (LQG), exploring concepts such as coherent states, semiclassical spacetime, and potential emergent quasi-particles. Participants examine theoretical implications and connections to quantum chaos, as well as the coupling of Standard Model quantum field theory to SF models.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- Some participants suggest that collective modes may emerge from the phase space of random lattices in SF, similar to phonons.
- Others propose that coherent states could be considered collective modes from the perspective of elementary excitations.
- There is uncertainty about whether the concept of collective excitations applies to SF, as some argue that SF does not "vibrate" but exists as a collective excitation on the vacuum.
- One participant mentions the possibility of quasi-particles emerging from strongly spin systems, likening them to spin waves.
- Discussion includes the analysis of kinematics and dynamics related to spin flips and propagation.
- Some participants inquire about the existence of semiclassical spacetime in SF models and reference related papers on coherent states and graviton propagators.
- Questions arise regarding the coupling of conventional Standard Model quantum field theory to SF models, with some noting existing derivations for scalars and vector particles but a lack of detailed derivations for fermions.
Areas of Agreement / Disagreement
Participants express differing views on the applicability of collective modes to SF, with no consensus on whether semiclassical spacetime exists in SF models. The discussion remains unresolved regarding the coupling of Standard Model QFT to SF models.
Contextual Notes
Limitations include the dependence on definitions of collective modes and semiclassical spacetime, as well as unresolved mathematical steps related to the coupling of theories.