If gravity is emergent, how does this affect string theory and loop quantum gravity?

[kodama]

TL;DR

From Quantum Relative Entropy to the Semiclassical Einstein Equations

the paper in

Physical Review Letters​

From Quantum Relative Entropy to the Semiclassical Einstein Equations​

Philipp Dorau* and Albert Much†

Abstract​

We provide arguments indicating that the semiclassical Einstein equations follow from quantum relative entropy and its proportionality to an area variation. Using modular theory, we establish that the relative entropy between the vacuum state and coherent excitations of a scalar quantum field on a bifurcate Killing horizon is given by the energy flux across the horizon. Under the assumption of the Bekenstein-Hawking entropy-area formula, this energy flux is proportional to a variation in the surface area of the horizon cross section. The semiclassical Einstein equations follow automatically from this identification. Our approach provides a quantum field theoretic generalization of Jacobson’s thermodynamic derivation of the Einstein equations, replacing classical thermodynamic entropy with the well-defined quantum relative (Araki-Uhlmann) entropy. This suggests that quantum information plays a central role in what is often seen as a zeroth order approximation of a theory of quantum gravity, namely quantum field theory in curved spacetimes.
Phys. Rev. Lett. 136, 091602 – Published 2 March, 2026

DOI:https://doi.org/10.1103/lmq8-nsty

this means gravity isn't a fundamental force

if true what does this means to string theory and loop quantum gravity and other quantum gravity?

are there gravitons in these theories

 

[Demystifier]

In such a theory there may still be a graviton, but in such a theory it is a collective excitation analogous to a phonon (a quantum of sound), rather than a fundamental particle. Such theories are in spirit very different from loop quantum gravity and string theory, but there is no direct contradiction between them. Loop quantum gravity, and even string theory, may well be good effective theories, rather than the fundamental ones.

 

[Demystifier]

Sabine also made a video on that paper: