Gravity has always been quantum mechanical: it is the wrong thing to quantise
6 hours ago
- #wave relativity
- #quantum gravity
- #no-hair theorem
- Gravity is inherently quantum mechanical, and the conventional quantum gravity program quantizes the wrong entity.
- A thought experiment comparing a star and a black hole with identical mass, charge, and angular momentum shows they are gravitationally indistinguishable at large distances due to the no-hair theorem, but their internal matter content differs drastically.
- The long-term gravitational dynamics, such as radiation and merger waveforms, depend on the internal evolution of the matter sector rather than just exterior properties.
- Classical mechanics treats objects as structureless, while quantum mechanics views structure as constitutive, involving internal symmetries, spinors, and mode towers.
- The quantum revolution from 1900–1928 redefined particles and fields from structureless to structurally constitutive, extending to quantum field theory and the vacuum.
- Gravity is sensitive to the structural details of the matter that sources it, even if it appears mass-blind at a distance, making it quantum mechanical in this new sense.
- Quantizing gauge fields is feasible because the source and field can be separated, but for gravity, the metric couples to the stress-energy tensor including self-stress, preventing clean separation.
- The essay proposes quantizing the matter sector, not the metric, as the correct approach, with the metric as a functional of a Dirac spinor field.
- A self-consistency equation relates the spinor field to the geometry it produces, recovering Einstein's equations at long wavelengths and quantum field theory from fluctuations.
- Open problems like the Hubble tension and information paradox motivate deeper quantization of matter rather than the gravitational field itself.