xTras:	a field theory inspired xAct package for Mathematica
Author:	Teake Nutma © 2012-2014 under GPL.
Article:	arXiv:1308.3493 [cs.SC]

Online documentation ▪ Release history ▪ Source code

Introduction

xTras is a field-theory inspired add-on package for xAct. 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. >>
• Computing equations of motion of monomials of Riemann tensors. >>
• Symmetrizing covariant derivatives. >>
• Perturbations around AdS spaces. >>
• Killing vectors. >>
• Young symmetrizers and projectors. >>
• Solving linear systems of tensorial equations. >>

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

Latest release: 1.4.2 (Oct 30, 2014)

What's new:

• Added RicciToRiemann.
• Added KretschmannToRiemann.
• ToRiemann also converts rank-2 curature tensors if the curvature relations are not enabled.
• ToRicci also converts contractions of Riemann tensors to Ricci tensors even if the curvature relations are not enabled.

The full release history can be found here.

Installation

xTras is not a stand-alone package. It depends on various packages contained in the main xAct bundle. In order to install xTras, do the following:

1. Download and install the latest main xAct bundle, which contains xTras, from here.
2. Download the Invar database and install it (instructions).

The premier support channel is the main xAct mailing list. If you find a bug, you can also report it over at xTras' Github issue tracker.

FAQ

Q: FullSimplification doesn't work and returns the RInv::nodatabase message. What's wrong?
A: FullSimplification needs the Invar database to work. Install it from http://xact.es/Invar/ and the message should go away.