A New Link Between Quantum Physics and Gravity

Quick Overview

A new paper suggests a method to link quantum physics and gravity by recalculating quantum corrections in general relativity, arguing that for nonlinear theories like GR, one must average the product of the metric tensor and its derivatives, not the product of the averages, which potentially makes quantum corrections significant on galactic scales due to the cosmological constant.

Key Points: Einstein's general relativity is strictly wrong because it does not account for quantum effects, even though quantum particles create gravitational fields. Previous calculations showing quantum gravity effects were too small to measure by a factor of 10 to the 20, rendering them experimentally unreachable. The new paper proposes that because general relativity is nonlinear, the average of the product of the metric tensor and its derivatives must be taken, rather than the product of the averages. The authors find that while quantum corrections remain tiny in the solar system, they can become large on the scales of galaxies due to a contribution from the cosmological constant. First author Ben Kau states that on cosmological scales, there is a "clear difference between the particle trajectories predicted by the quantized new equations and those obtained from unquantized general relativity." The presented work is not a full theory of quantum gravity but a formalism linking such a theory to observations, requiring an input describing the quantum state of space and time. The reviewer rates the paper a three out of ten, finding it formally correct but questioning the claim of a clear difference at large distances based on the provided text.

Context: The video discusses a new physics paper attempting to bridge the 90-year gap between Einstein's General Relativity (GR) and quantum mechanics, a problem known as quantum gravity. GR accurately describes gravity on large scales but lacks quantum effects, which are necessary because quantum particles generate gravity. The core challenge has been that theoretical quantum corrections to GR are calculated to be far too small to ever be experimentally tested.