Dimensional reduction in numerical relativity: Modified Cartoon formalism and regularization

Abstract

We present in detail the Einstein equations in the Baumgarte–Shapiro–Shibata–Nakamura formulation for the case of [Formula: see text]-dimensional spacetimes with [Formula: see text] isometry based on a method originally introduced in Ref. 1. Regularized expressions are given for a numerical implementation of this method on a vertex centered grid including the origin of the quasi-radial coordinate that covers the extra dimensions with rotational symmetry. Axisymmetry, corresponding to the value [Formula: see text], represents a special case with fewer constraints on the vanishing of tensor components and is conveniently implemented in a variation of the general method. The robustness of the scheme is demonstrated for the case of a black-hole head-on collision in [Formula: see text] spacetime dimensions with [Formula: see text] symmetry.