$mathtt{bimEX}$: A Mathematica package for exact computations in 3$+$1 bimetric relativity. (arXiv:1904.10464v1 [cs.SC])
<a href="http://arxiv.org/find/cs/1/au:+Torsello_F/0/1/0/all/0/1">Francesco Torsello</a>

We present $mathtt{bimEX}$, a Mathematica package for exact computations in
3$+$1 bimetric relativity. It is based on the $mathtt{xAct}$ bundle, which can
handle computations involving both abstract tensors and their components. In
this communication, we refer to the latter case as concrete computations. The
package consists of two main parts. The first part involves the abstract
tensors, and focuses on how to deal with multiple metrics in $mathtt{xAct}$.
The second part takes an ansatz for the primary variables in a chart as the
input, and returns the covariant BSSN bimetric equations in components in that
chart. Several functions are implemented to make this process as fast and
user-friendly as possible. The package has been used and tested extensively in
spherical symmetry and was the workhorse in obtaining the bimetric covariant
BSSN equations and reproducing the bimetric 3$+$1 equations in the spherical
polar chart.

We present $mathtt{bimEX}$, a Mathematica package for exact computations in
3$+$1 bimetric relativity. It is based on the $mathtt{xAct}$ bundle, which can
handle computations involving both abstract tensors and their components. In
this communication, we refer to the latter case as concrete computations. The
package consists of two main parts. The first part involves the abstract
tensors, and focuses on how to deal with multiple metrics in $mathtt{xAct}$.
The second part takes an ansatz for the primary variables in a chart as the
input, and returns the covariant BSSN bimetric equations in components in that
chart. Several functions are implemented to make this process as fast and
user-friendly as possible. The package has been used and tested extensively in
spherical symmetry and was the workhorse in obtaining the bimetric covariant
BSSN equations and reproducing the bimetric 3$+$1 equations in the spherical
polar chart.

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