Intro
Invar` is currently a package for efficient simplification of the algebraic and differential polynomial scalars (usually known as invariants) of the Riemann tensor of a metric-compatible connection. The medium term goal is generalizing Invar` to simplify generic polynomial expressions (with free indices) of the Riemann tensor.
Invar` requires the tensor computer algebra system xTensor` when running on Mathematica. There is a twin version for Maple, based on the tensor system Canon. It can be downloaded, under the General Public Licence, from
http://metric.iem.csic.es/Martin-Garcia/xAct/
http://www.lncc.br/~portugal/ (Maple version)
For further information, see the articles
The Invar tensor package, J.M. Martín-García, R. Portugal and L.R.U. Manssur, Comp. Phys. Comm. 177, 640 (2007)
The Invar tensor package: Differential invariants of Riemann, J.M. Martín-García, D. Yllanes and R. Portugal, Comp. Phys. Comm. (2008)
Subsection 6.3 contains a number of tests designed to check most capabilities of Invar`. They all should give zero.
Load the package and configure
2. General concepts and definitions
4. Inv -> Permutation -> Riemann
5. Riemann -> Permutation -> Inv
7. Working with order 12 invariants
8. The (algebraic) Narlikar and Karmarkar basis
| Created by Mathematica (May 16, 2008) | |