The discussion centers on the quantum mechanics of entropic forces, particularly the idea that gravity may emerge from the entropic rearrangement of information. Participants explore the implications of this conjecture, referencing historical contributions and theoretical models, including the work of Jacobson on black hole entropy and its relation to gravity.
Participants express differing views on the implications of Jacobson's work and the nature of gravity as entropic. The discussion remains unresolved, with multiple competing interpretations of the relationship between entropy, temperature, and gravity.
There are unresolved assumptions regarding the definitions of entropy and temperature in the context of general relativity and quantum mechanics. Participants highlight the need for clarity on the predictions made by various models and their experimental verification.
Abstract
It was conjectured 30 years ago that gravity could arise from the entropic rearrangement of information. We offer a set of microscopic quantum models which realize this idea in detail. In particular, we suggest a simple mechanism by which Newton’s law of gravity arises from extremization of the free energy of a collection of qubits or oscillators, rather than from the exchange of virtual quanta of a fundamental field. We give both a local and a nonlocal version of the construction and show how to distinguish a range of these entropic models from ordinary perturbative quantum gravity using existing observations and near-term experiments.
Phys. Rev. X 15, 031038 – Published 11 August, 2025
How did he prove it?Chiara said:The abstract starts with "It was conjectured 30 years ago that gravity could arise from the entropic rearrangement of information."
It seems to me that Jacobson proved that gravity is entropic. He did not conjecture anything. Am I wrong?
That doesn't prove that his model is correct. Until the model makes predictions that are different from other models, and experiments show that those predictions are correct, the model is just a hypothesis. That's how science works.Chiara said:He showed in his paper that the entropy of black holes, their temperature, and their mass/energy, taken together, imply the field equations. Here is his 1995 paper: https://arxiv.org/abs/gr-qc/9504004
This is not a prove that gravity is entropic. It is a prove that the field quations are equvalent to something else.Chiara said:Jacobson gave a purely mathematical proof: the entropy of black holes, their temperature, and their mass/energy, taken together, imply the field equations.
That is not true, is it? General relativity doesn't predict enything like that. Or can you show us that prediction?Chiara said:Various experiments, e.g. about Unruh temperature, imply that black holes have a temperature.
General relativity predicts that black hole entropy and temperature vanish.
Jacobson's approach disagrees with general relativity but agrees with data.
It does no such thing. GR says nothing whatever either way about black hole entropy and temperature. Temperature and entropy don't even appear in the Einstein Field Equation.Chiara said:General relativity predicts that black hole entropy and temperature vanish.