Existing examples

Binary Black Hole example

The initial conditions consist in a superposition of two boosted black holes. The example uses an approximation for low boosts to solve the Hamiltonian constraint which is accurate up to order P^4.

The example can optionally be run using initial data from our standalone version of the TwoPunctures code. The TwoPunctures code is kept in a separate repository for licensing reasons. Instructions are provided in the README explaining how to build the BinaryBH example with TwoPunctures.

See Running the BinaryBH example for more details on this Example.

Kerr BH example

This is a stationary Kerr solution for high spin black holes, based on the semi isotropic Kerr-Schild coordinates proposed by Brandt and Seidel and revised by Liu, Etienne and Shapiro.

The evolution seen initially is simply the gauge evolution as the analytic initial data settles into the puncture gauge of the evolution - try visualising the conformal factor chi to see this.

The example is very minimal and is a good starting point for single black hole vacuum spacetimes.

Scalar Field example

This example takes the KerrBH example and adds in a scalar field as matter content in the evolution.

The initial conditions are a single Kerr black hole immersed in a scalar field background which asymptotes to a constant density value. The goal is to show how matter can be included in the evolution.

This example temporarily turns off the coupling between matter and the metric (setting G_Newton = 0.0) since the initial conditions do not satisfy the Hamiltonian and Momentum constraints. One can instead set G_Newton = 1.0 to reinstate the coupling, and use CCZ4 damping to reduce the violation of the constraints over time, but we would recommend instead using the Initial Condition Solver to generate sensible initial data.

We plan to update this to provide an Oscillaton as an example in due course, in which case numerical data for the constraint satisfying profile will be included.