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Compute ADM momenta as volume integrals #6433

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Proposed changes

This PR improves the accuracy of P_ADM and J_ADM by computing them as a sum of infinite volume integrals and finite surface integrals, which were derived from the standard ADM equations using Gauss' Law. We have attempted to use this same trick for other asymptotic quantities (ADM mass/energy and center of mass), but the volume version didn't improve accuracy. This is evident from the convergence plot below, in which the CoM volume results have been omitted because of blow-ups.

resolution_convergence_with_Jadm

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  • The code is documented and the documentation renders correctly. Run
    make doc to generate the documentation locally into BUILD_DIR/docs/html.
    Then open index.html.
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    code review guide.
  • The PR lists upgrade instructions and is labeled bugfix or
    new feature if appropriate.

Further comments

// Skip interfaces not at the outer boundary
if (boundary_direction != Direction<3>::upper_zeta()) {
continue;
// Interfaces at the inner boundary
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You can do this to avoid duplicating all these projections:

if (boundary_direction.dimension() != 2) {
  continue;
}
// Do projections

@@ -54,7 +54,7 @@ void test_local_adm_integrals(const double& distance,
const std::vector<double>& prev_distances) {
// Define black hole parameters.
const double mass = 1;
const double boost_speed = 0.5;
const double boost_speed = 0.;
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Is this change needed?

@@ -198,6 +198,8 @@ void test_local_adm_integrals(const double& distance,
deriv_conformal_metric, inv_conformal_metric);
const auto conformal_christoffel_contracted = tenex::evaluate<ti::i>(
conformal_christoffel_second_kind(ti::J, ti::i, ti::j));
const auto deriv_conformal_christoffel_second_kind = partial_derivative(
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Do you need this and the longitudinal shift, Ricci additions below?

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2 participants