A Gravity in the Thermal Interpretation

Messages
48,827
Reaction score
24,954
TL;DR Summary
Does gravity need to be quantized in the thermal interpretation of QM?
This question is mainly for @A. Neumaier, but I post it in public in case others are interested.

The usual reason given for needing to quantize gravity is, heuristically, that, in the presence of quantized stress-energy where there can be a superposition of different stress-energy tensors, there must also be a superposition of different spacetime geometries.

One proposal for avoiding having to do this, at least as an approximation, is the "semiclassical" Einstein Field Equation, where the spacetime geometry is still treated classically, and the source on the RHS of the Einstein Field Equation is the expectation value of the stress-energy tensor. This is normally considered an approximation because in QM expectation values are normally not considered as fundamental.

In the thermal interpretation of QM, however, q-expectations are considered fundamental "beables". That raises an obvious question: would the "semiclassical" EFE even need to be treated as an approximation in the thermal interpretation? Or could it be considered as the fundamental equation of gravity, since the q-expectation of the stress-energy tensor is considered a fundamental "beable" in this interpretation? In short, would this remove the need to quantize gravity in the thermal interpretation?

[1] https://www.physicsforums.com/threads/the-thermal-interpretation-of-quantum-physics.967116/
 
Physics news on Phys.org
PeterDonis said:
In the thermal interpretation of QM, however, q-expectations are considered fundamental "beables". That raises an obvious question: would the "semiclassical" EFE even need to be treated as an approximation in the thermal interpretation? Or could it be considered as the fundamental equation of gravity, since the q-expectation of the stress-energy tensor is considered a fundamental "beable" in this interpretation? In short, would this remove the need to quantize gravity in the thermal interpretation?
Semiclassical gravity is consistent in the thermal interpretation, as is any mixed quantum-classical dynamics following standard patterns. (See Section 7.8 of my book.)

Thus there is no absolute need for quantizing gravity. However, since all other quantum-classical dynamical systems studied are approximations of a more fundamental purely quantum dynamical system, it appears very likely (to me, on the grounds of beauty and uniformity) that the same holds for quantum gravity.
 
I would like to know the validity of the following criticism of one of Zeilinger's latest papers https://doi.org/10.48550/arXiv.2507.07756 "violation of bell inequality with unentangled photons" The review is by Francis Villatoro, in Spanish, https://francis.naukas.com/2025/07/26/sin-entrelazamiento-no-se-pueden-incumplir-las-desigualdades-de-bell/ I will translate and summarize the criticism as follows: -It is true that a Bell inequality is violated, but not a CHSH inequality. The...
I understand that the world of interpretations of quantum mechanics is very complex, as experimental data hasn't completely falsified the main deterministic interpretations (such as Everett), vs non-deterministc ones, however, I read in online sources that Objective Collapse theories are being increasingly challenged. Does this mean that deterministic interpretations are more likely to be true? I always understood that the "collapse" or "measurement problem" was how we phrased the fact that...
This is not, strictly speaking, a discussion of interpretations per se. We often see discussions based on QM as it was understood during the early days and the famous Einstein-Bohr debates. The problem with this is that things in QM have advanced tremendously since then, and the 'weirdness' that puzzles those attempting to understand QM has changed. I recently came across a synopsis of these advances, allowing those interested in interpretational issues to understand the modern view...

Similar threads

Back
Top