xTras

xTras is a field-theory inspired add-on package for xAct, the state-of-the-art tensor calculus package for Mathematica.

Some of the extra functionality it brings is:

• Generating a list of all contractions of a given tensorial expression.
• Generating lists of dimensional dependent identities (e.g. the vanishing of the Weyl tensor in D=3).
• Making any tensorial expression traceless.
• Symmetrizing covariant derivatives.
• Computing equations of motion of monomials of Riemann tensors.
• Perturbations around AdS spaces.
• Killing vectors.
• Easy access to the database of the Invar package.
• Young symmetrizers and projectors.
• Solving linear systems of tensorial equations, both for constant variables (SolveConstants) and for tensors (SolveTensors).

For more information, have a look at the associated publication or at the online documentation.

Installation

Installing the package in Mathematica

If you just want to run the xTras package as a end user, download the compiled zip file from http://www.xact.es/xtras, unzip, and follow the instructions.

Configuring the project in Wolfram Workbench

If you want to set up xTras in Workbench to edit the code, you'll have to take a few extra steps. This assumes you already have a Workbench environment up and running.

1. Download and install the complete xAct bundle where Mathematica can find it, but remove or rename the xAct/xTras/ subdirectory.
2. Checkout or download the xTras source, and import it in Workbench.
3. Edit the file buildfiles/main.xml such that properties in the section Machine-specific config variables match your setup.

Running notebooks for testing code is the same as usual, but deploying and building the documentation is not, due to xTras' unusual structure (it's a sub-package for xAct, which isn't supported out-of-the-box in Workbench). Deploying can be done by running the deploy target in the buildfiles/main.xml file, and building the documentation by running the documentation target. The complete project can by build by running the all target. Be sure to set the Runtime JRE to Separate JRE in the JRE tab of the Eclipse external tools configuration of the Ant targets.

The unit tests can be run by running the tests/TestSuite.mt as a Mathematica Test.

What's what

The Workbench project is structured into the following directories:

buildfiles/       Ant files for building the docs, changelog, and the distributable zip.
notebooks/        Mathematica *.nb files to run and / or test code.
tests/            Unit test files.
xAct/             The actual code of the package.
xTras/            Documentation source.