Can soft gravitational charges carry the information of an evaporating black hole?
In plain words
A black hole can carry tiny extra charges tied to zero-energy gravitons and photons, called soft hair. The question is whether this hair can store enough information to make evaporation information-preserving.
Precise statement
Supertranslation and superrotation (BMS) charges and the associated soft graviton modes at the horizon and null infinity were proposed as information carriers (Hawking, Perry, Strominger 2016). Count the independent soft-hair states accessible to a Schwarzschild black hole of mass M in the semiclassical regime and determine whether they can purify the Hawking radiation, i.e. carry of order $A c^{3}/(4 G \hbar)$ units of entropy correlated with the hard quanta. Answer yes or no with the entropy count.
What would settle it
A computation of the entanglement between soft modes and hard Hawking quanta over the full evaporation, compared with the Bekenstein-Hawking entropy.
Status in the literature
Unverified note
Several analyses argue soft modes decouple from hard Hawking quanta and cannot purify the radiation; no accepted count shows otherwise as of 2026.