A post-quantum theory of classical gravity?

A post-quantum theory of classical gravity?
Jonathan Oppenheim, University College London
Physics Colloquium 2019-11-28

Can one have a consistent theory of classical systems coupled to quantum ones? Yes. We construct a theory of classical gravity coupled to quantum field theory. The theory doesn't suffer the pathologies of semi-classical gravity and reduces to Einstein's equations in the appropriate limit. The assumption that gravity is classical necessarily modifies the dynamical laws of quantum mechanics -- the theory must be fundamentally information destroying involving finite sized and stochastic jumps in space-time and in the quantum field. The measurement postulate of quantum mechanics is not needed since the interaction of the quantum degrees of freedom with classical space-time necessarily causes collapse of the wave-function. The theory can be regarded as fundamental, or as an effective theory of the backreaction of quantum fields on space-time.

[bartbozon]

Probably gaining some traction now....

[TomMannHome]

Both the video & audio are glitching. In some spots, this makes it very hard to follow the lecture. They need to fix this. PS - I’m watching this on a very fast fiber feed & I don’t see this problem on any other videos, so it’s almost certainly a problem with what was uploaded, not at my end.

[Achrononmaster]

@13:00 Feynman's argument was erroneous, far too idealistic. Many people have pointed out before that in classical mechanics we have measurement limits too, but they are not so crisp, they are operational, you can think of it as ħ → 0 but not ħ =0. The reason is because matter is clumpy, which is really a "quantum" postulate, but CM has to use it or it cannot well-describe the world. However, it is also erroneous to assume the Moon can be placed into superposition. It's atomic parts can, but maybe not the whole thing. That "maybe not" is critical, if it holds then Feynman's argument does not work. A Moon or large rock will always go through only one slit and you'll never see interference. That can be a prediction of JO's team's theory (and many other gravity theories too that admit classical--quantum coupling, like Gauge Gravity in the STA).

[tixch]

where does the stochasticity comes from?

[buddha-chris]

Amazing work! Noble for sure, if this theory is proven 👍 Wow!

[traruhsynred]

It seems wrong to me that the notion that the superposition of the moon on the left and moon on the right is equivalent to 1/2/moon on the left and 1/2 moon on the right is wrong. It's a superposition of orthogonal states and just as with spin, if you do a measurement (like dropping a test mass) you will get one or the other not some combination.

[traruhsynred]

I don't get why there a 'black hole' information paradox. Since black hole horizons take forever to form for an external observer the paradox never occurs.

[pacman-xm]

So if matter remains quantum and space-time classical, and both at the end are expressions of the same, how happens that transition?

[SOJACjac]

I've been saying for 20 years it doesn't make sense to quantize gravitation

[PrivateSi]

It does it both ways, believe me, as a Centrist debater. The only properly proven boson is indeed The Photon, and it carried the EM 'force', and the electric force is the base force, all other 'forces' are emergent. There is a unified field of 2 particles, + and - cells in superposition forming +- cells that can be split, bonding to neighbours to form a positron (+-+) and electron (-+-)... Next level is proton (pep) and anti-proton (epe).. Neutron (pep_e).. Beta- decay = pep_e => pep e...
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Beta+ 'decay' = NEW e_p pair with the electron retained (pep_e) and proton expelled.. Muon (ep_e, anti pep_p).. Tau (epep_e, anti pepe_p), Kaons / Pions as some combination of, + and + (non-split) free cells that turn back into balanced, +- field. Neutral, empty field has no resistance, gravity and part of the strong force is the field inwardly repelling matter= broken free field.. Mathematicians who can be bothered should be able to GUTOE it with a bit of sums.
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POLECTRON FIELD: cell: a + & a - particle split by Full Split Energy as a positron+ & electron-. Bonds to 12 neighbours
MATTER: p+ / e- = 1.5 cells, +−+ /−+−. Splits field into + & − shells. particle bits: free +, −, +−
SPIN: centre polarisation axis
LECKY: absolute charge.
MASS: particle lecky.
INERTIA: rebalancing field kicks mass.
STRONG GRAVITY: field repels mass
MOND: lecky density slows acceleration/TIME and shrinks cells, loss to gravity gradients grows voids, aids acceleration
BIG BANG: more proton-antiproton pairs malformed as proton-muon than antiproton-antimuon so hydrogen beat antihydrogen
POSITRONIUM: e_p. Muon: ep_e. Proton: pep. Neutron: pep_e. Tau: epep_e. Neutron mass is halfway between muon and tau
ANTIMATTER: 1, 2 e_p pairs annihilate. 3: proton+anti proton or muon+anti muon. 4: neutron+anti neutron. 5: tau+anti tau
WEAK FORCE: unstable atoms form and annihilate e_p pairs.
BETA- DECAY: pep_e => pep e.
BETA+: pep + new e_p => pep_e p
NUCLEAR FORCE: neutron electrons bond to protons.
ENTANGLEMENT: correlation broken by interaction? Physical link?
BLACK HOLE: atoms cut into neutrons fused as higher mass tau cores (epep). Field rotates. Core annihilates: ep => cell?
PHOTON: cell polarisation/lateral shift wave.
LONGITUDINAL WAVE: gravitational wave, neutrino: 1 to 3 cell wave
DOUBLE SLIT: photon/particle field warps diffract and interfere, guiding the core. Detectors interfere with guides
COMPLEXITY: Closed system complexity reduces over time. Uniformly (dis)ordered (hot)/cold field is simplest

[Achrononmaster]

@4:00 There is more nuance than Jonathan provides. If you wish a more natural physics, and accept *_global_* spacetime is distinct to *_local_* matter, so GR is not going to get quantised, there is a remaining problem, which is what the heck is matter, and why does it couple to spacetime (i.e., why is gravity a thing?) The obvious answer is they are not entirely different, matter _is_ spacetime, but with local symmetry (local rotations between states). But that gives you a completely different fresh perspective - you realise gravity was always quantum mechanical, because particles are topological defects in spacetime, they have to be★, if they couple to gravity/geometry.
★ Otherwise you are doing magical metaphysics, like Newton, with angels, or whatever, responsible for ensuring things behave according to the sterile mathematical cosmic rulebook.