On Monday, October 28, 2019 at 1:19:02 AM UTC-5, John Clark wrote: > > On Sun, Oct 27, 2019 at 12:04 PM Lawrence Crowell < > [email protected] <javascript:>> wrote: > > *> Quantum mechanics makes no particular prediction on the continuity of >> spacetime. If one equates the Schwarzschild radius with a Compton >> wavelength you get the Planck scale of 1.6x10^{-35}m. However, this really >> just tells us one is not able to locate a qubit in a region smaller than >> this scale.* > > > If you can't put a particle or a wave or a qubit in less than 1.6x10^{-35}m > then what can you put in there, and in what sense is it meaningful to say > spacetime is smooth? > > John K Clark > > It still is a problem being worked on.
https://arxiv.org/abs/1812.11450 Spin-Spacetime Censorship Jonathan Nemirovsky <https://arxiv.org/search/gr-qc?searchtype=author&query=Nemirovsky%2C+J>, Eliahu Cohen <https://arxiv.org/search/gr-qc?searchtype=author&query=Cohen%2C+E>, Ido Kaminer <https://arxiv.org/search/gr-qc?searchtype=author&query=Kaminer%2C+I> (Submitted on 30 Dec 2018 (v1 <https://arxiv.org/abs/1812.11450v1>), last revised 7 Oct 2019 (this version, v2)) Quantum entanglement and relativistic causality are key concepts in theoretical works seeking to unify quantum mechanics and gravity. In this article, we show that the interplay between relativity theory and quantum entanglement has intriguing consequences for the spacetime surrounding elementary particles with spin. Classical and quantum gravity theories predict that a spin-generated magnetic dipole field causes a (slight) bending to the spacetime around particles, breaking its spherical symmetry. Motivated by the apparent break of spherical symmetry, we propose a very general gedanken experiment that does not rely on any specific theory of classical or quantum gravity, and analyze this gedanken experiment in the context of quantum information. We show that any spin-related deviation from spherical symmetry would violate relativistic causality. To avoid the violation of causality, the measurable spacetime around the particle's rest frame must remain spherically symmetric, potentially as a back-action by the act of measurement. This way, our gedanken experiment proves that there must be a censorship mechanism preventing the possibility of spacetime-based spin detection, which sheds new light on the interface between quantum mechanics and gravity. We emphasize that our proposed gedanken experiment is independent of any theory and by allowing spacetime to be quantized its purpose is to be used for testing present and future candidate theories of quantum gravity. @philipthrift -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/cd6312f0-c036-4e8a-b449-efc3abfa58dd%40googlegroups.com.
