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No no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitati

No no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitational lensing. Since gravitational lensing is a real effect that we have clearly seen, it means that QM as it exists today is just wrong (in its predictions about how light moves around the sun). GR does of course predict gravitational lensing. However, if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment, the solution would show two different bright spots, corresponding to the two slits; in reality, we see an interference pattern. So GR is also wrong. By definition, a (correct) theory of quantum gravity would predict both gravitational lensing and the way photons behave in a dobule-slit experiment (otherwise, we would say that either the theory is wrong, or it is not a theory of quantum gravity). However, no such theory exists today, at least none that doesn't contradict other observations.

raattgift 3y ago
There are already experiments (and simulations) which show Raychaudhuri focusing and Einstein lensing in purely-quantum analog gravity (see e.g. <https://scitechdaily.com/bridging-quantum-theory-and-relativity-curved-spacetime-in-a-quantum-simulator/ https://scitechdaily.com/bridging-quantum-theory-and-relativ...> for something moderately accessible that allows for attaching a causal cone at each point in a relevant analog spacetime), so > no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitational lensing falls down because we can describe such an effect purely quantum mechanically. Also, I think you should be put to proof with respect to a claim against quantum perturbative or canonical methods in the solar-mass lensing regime in which perturbation theory works great for classical GR, taking into account all sorts of beyond-leading-order (classical) effects like noncircularity, backreaction, helicity, you name it. The sun is a fixed enough background that it's a linearized gravity problem. What exactly in "QM as it exists today" breaks (or is broken by) this? > ... if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment ... GR is also wrong. How exactly does taking the fully Lorentz-invariant QED or Standard Model to local Lorentz-invariance (with the radius of curvature significantly larger than the laboratory experiment) break the picture? We are nowhere near needing to consult Birrell & Davies. What do you think needs doing here if "you used the formulae of GR", beyond solving the EFEs and the geodesic equations for the whole (region of) spacetime, and then wondering what geodesic any given photon will couple to? What do you think the scale of the correction from Minkowskian geodesics will be? And how much of that do you impute to the apparatus?

raattgift 3y ago

There are already experiments (and simulations) which show Raychaudhuri focusing and Einstein lensing in purely-quantum analog gravity (see e.g. <https://scitechdaily.com/bridging-quantum-theory-and-relativity-curved-spacetime-in-a-quantum-simulator/ https://scitechdaily.com/bridging-quantum-theory-and-relativ...> for something moderately accessible that allows for attaching a causal cone at each point in a relevant analog spacetime), so > no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitational lensing falls down because we can describe such an effect purely quantum mechanically. Also, I think you should be put to proof with respect to a claim against quantum perturbative or canonical methods in the solar-mass lensing regime in which perturbation theory works great for classical GR, taking into account all sorts of beyond-leading-order (classical) effects like noncircularity, backreaction, helicity, you name it. The sun is a fixed enough background that it's a linearized gravity problem. What exactly in "QM as it exists today" breaks (or is broken by) this? > ... if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment ... GR is also wrong. How exactly does taking the fully Lorentz-invariant QED or Standard Model to local Lorentz-invariance (with the radius of curvature significantly larger than the laboratory experiment) break the picture? We are nowhere near needing to consult Birrell & Davies. What do you think needs doing here if "you used the formulae of GR", beyond solving the EFEs and the geodesic equations for the whole (region of) spacetime, and then wondering what geodesic any given photon will couple to? What do you think the scale of the correction from Minkowskian geodesics will be? And how much of that do you impute to the apparatus?