xTras: A field-theory inspired xAct package for mathematica

Abstract We present the tensor computer algebra package xTras , which provides functions and methods frequently needed when doing (classical) field theory. Amongst others, it can compute contractions, make Ansatze, and solve tensorial equations. It is built upon the tensor computer algebra system xAct , a collection of packages for Mathematica. Program summary Program title: xTras Catalogue identifier: AESH_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AESH_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 155 879 No. of bytes in distributed program, including test data, etc.: 565 389 Distribution format: tar.gz Programming language: Mathematica. Computer: Any computer running Mathematica 6 or newer. Operating system: Linux, Unix, Windows, OS X. RAM: 100 Mb Classification: 5. External routines: xACT ( www.xact.es ) Subprograms used: Cat Id Title Reference AEBH_v1_0 xPerm CPC 179 (2008) 597 ADZK_v2_0 Invar Tensor Package 2.0 CPC 179 (2008) 586 Nature of problem: Common problems in classical field theory: making Ansatze, computing contractions, solving tensorial equations, etc. Solution method: Various (group theory, brute-force, built-in Mathematica functions, etc.) Running time: 1–60 s