I On the Quantum Mechanics of Entropic Forces

[kodama]

TL;DR

it from bit

On the Quantum Mechanics of Entropic Forces​

Daniel Carney1,*, Manthos Karydas1, Thilo Scharnhorst1,2, Roshni Singh1,2, and Jacob M. Taylo

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

DOI: https://doi.org/10.1103/y7sy-3by1

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could spin foam also work ?

 

[Neutrin0]

Spin foam could work I’m around half way done reading the paper. but to prove spin foam would take a lot of time to solve the theoretical hurdles one would face and to actually do experiments

 

[Chiara]

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?

 

[martinbn]

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?

How did he prove it?

 

[Chiara]

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

 

[PeterDonis]

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

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]

Jacobson gave a purely mathematical proof: the entropy of black holes, their temperature, and their mass/energy, taken together, imply the field equations.

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.

 

[weirdoguy]

What data?

 

[martinbn]

Jacobson gave a purely mathematical proof: the entropy of black holes, their temperature, and their mass/energy, taken together, imply the field equations.

This is not a prove that gravity is entropic. It is a prove that the field quations are equvalent to something else.

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.

That is not true, is it? General relativity doesn't predict enything like that. Or can you show us that prediction?

 

[Chiara]

"Black" means: "It does not shine". This is the prediction of general relativity.

A non-zero BH temperature means: it does shine, it is not black. That was the discovery.

By the way: "Jacobson gave a purely mathematical proof: the entropy of black holes, their temperature, and their mass/energy, taken together, imply the field equations." The opposite direction is not true - obviously.

To circle back to the OP: The statement "It was conjectured 30 years ago that gravity could arise from the entropic rearrangement of information." is not exactly what Jacobson proved. He proved that entropy, temperature, and energy of black holes can arise from the microscopic degrees of freedom of horizons and of space.

 

[PeterDonis]

General relativity predicts that black hole entropy and temperature vanish.

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.

 

[PeterDonis]

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