TECH Signal 500
Paper derives semiclassical Einstein equations from quantum relative entropy on bifurcate Killing horizons
↗
Illustration only Photo by Alexandre Debiève on Unsplash
A paper by Philipp Dorau and Albert Much argues that the semiclassical Einstein equations follow from quantum relative entropy, using modular theory to link relative entropy to energy flux across a horizon.
This work generalizes Jacobson's thermodynamic derivation of the Einstein equations by replacing classical thermodynamic entropy with quantum relative (Araki-Uhlmann) entropy, suggesting quantum information is central to quantum field theory in curved spacetimes. For researchers in quantum gravity and high-energy theory, it offers a quantum field theoretic pathway to equations usually treated as a zeroth-order approximation.
Written by elseif from the cluster below · every claim links back to a sourceThe three things worth knowing
The authors use modular theory to show relative entropy between the vacuum state and coherent excitations of a scalar quantum field on a bifurcate Killing horizon equals energy flux across the horizon.
Assuming 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, generalizing Jacobson's thermodynamic derivation with quantum relative entropy.
THE CLUSTER