The Black Hole information problem: past, present, and future
Donald Marolf
TL;DR
The paper surveys the black hole information problem, detailing how Hawking radiation’s near-thermal entanglement with interior states threatens unitarity during evaporation. It reviews a spectrum of resolutions, from microstate counting in holography (supporting unitary evolution) to dramatic departures from effective field theory or quantum mechanics (firewalls, nonlocality, ER=EPR, or nonlinear QM). It emphasizes the Page time as a crucial constraint and discusses why many EFT-based remedies fail for generic states. The discussion foregrounds the fruitful interplay between gravity and quantum information, suggesting that holographic ideas and error-correcting concepts will shape the path forward.
Abstract
We give a brief overview of the black hole information problem emphasizing fundamental issues and recent proposals for its resolution. The focus is on broad perspective and providing a guide to current literature rather than presenting full details. We concentrate on resolutions restoring naive unitarity.