Trapping Horizons as inner boundary conditions for black hole spacetimes

Understand

We present a set of inner boundary conditions for the numerical construction of dynamical black hole space-times, when employing a 3+1 constrained evolution scheme and an excision technique.

• These inner boundary conditions are heuristically motivated by the dynamical trapping horizon framework and are enforced in an elliptic subsystem of the full Einstein equation.
• In the stationary limit they reduce to existing isolated horizon boundary conditions.
• A characteristic analysis completes the discussion of inner boundary conditions for the radiative modes.