Is it necessary to quantize the gravitational field? The analogous question for the electrodynamic field was settled in a famous paper by Bohr and Rosenfeld, now almost 90 years ago. The answer is yes, as otherwise there would be a a way to bypass the Heisenberg uncertainty relations for a body obeying quantum mechanics and interacting with the field.
The gravitational question has been discussed for a long time, with opposite opinions appearing in the literature until very recently. I will discuss that one class of recently proposed Gedankenexperiments do not settle the issue, as a putative paradox (to be described in the talk) can be resolved by the simpler assumption that length scales below the Planck length can not be resolved. That the Gedankenexperiemnt does not imply quantization of the gravitational field of course does not imply the opposite, i.e. that gravitation is not quantized (i). It could also be that that the gravitational field is quantized anyway (ii), or that gravitation is somehow quantized, but is not as a quantum field theory (iii).
In the second part of the talk I will discuss an idea related to option (iii), motivated by Hawking’s paper ”Information Preservation and Weather Forecasting for Black Holes” (2014).
The talk is based on joint work with Erik Rydving and Igor Pikovski [first part, arXiv:2107.07514] and Michal Eckstein and Pawel Horodecki [second part, Foundations of Physics 51 (2), 1-13 (2021)].
Kollektorn, lecture room, Kemivägen 9, MC2-huset
29 October, 2021, 10:00
29 October, 2021, 11:00