Princeton University Gravity Initiative Seminar Series

Abstract: In gravity, spacelike separated regions can be dependent on each other due to the constraint equations. I my talk, I will propose a natural definition of subsystem independence in classical gravity.  Next, I show that extremal surfaces, generic trapped surfaces, andnon-perturbative lumps of matter appear as features enabling subregion independence.  For extremal surfaces, the underlying reason is that localized perturbations on one side of the surface contribute negatively to the mass on the other side, making the gravitational constraints behave as if there exist both negative and positive energy densities. This suggest a simple intuitive picture for why extremal surfaces tend to separate independent subsystems.  It also supports the consistency of islands in massless gravity and provide hints on the nature of the split property in perturbatively quantized general relativity. I also present novel area bounds for extremal surfaces in asymptotically de Sitter spacetimes.