Quantum Hair from Gravity

TL;DR

The paper investigates how the quantum state of a compact matter source relates to its asymptotic graviton field, introducing the concept of quantum hair. It shows that graviton states are energy-dependent and that semiclassical sources produce entangled graviton states with the interior, using an effective action to derive composition-dependent memory terms at order $r^{-3}$ and $r^{-5}$. The exterior metric can carry information about interior structure, leading to a memory effect and potential implications for Hawking radiation and black hole information. The work ties these quantum-gravitational memory effects to holographic ideas, suggesting that bulk interior information can be encoded in boundary graviton states within an EFT framework.

Abstract

We explore the relationship between the quantum state of a compact matter source and of its asymptotic graviton field. For a matter source in an energy eigenstate, the graviton state is determined at leading order by the energy eigenvalue. Insofar as there are no accidental energy degeneracies there is a one to one map between graviton states on the boundary of spacetime and the matter source states. A typical semiclassical matter source results in an entangled asymptotic graviton state. We exhibit a purely quantum gravitational effect which causes the subleading asymptotic behavior of the graviton state to depend on the internal structure of the source. These observations establish the existence of ubiquitous quantum hair due to gravitational effects.