xTras: A field-theory inspired xAct package for mathematica

This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018) 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 Ansätze, and solve tensorial equations. It is built upon the tensor computer algebra system xAct, a collection of packages for Mathematica. Title of program: xTras Catalogue Id: AESH_v1_0 Nature of problem Common problems in classical field theory: making Ansätze, computing contractions, solving tensorial equations, etc. Versions of this program held in the CPC repository in Mendeley Data AESH_v1_0; xTras; 10.1016/j.cpc.2014.02.006本程序源自贝尔法斯特女王大学（Queen's University Belfast）馆藏的CPC程序库（1969-2018）。 摘要 本文介绍张量计算机代数包xTras，其提供了开展（经典）场理论研究时常用的函数与方法。该包可完成张量缩并、构建试探假设（Ansatz）以及求解张量方程等操作。它基于面向Mathematica的张量计算机代数系统xAct开发，xAct是一套程序包集合。 程序名称：xTras 目录编号：AESH_v1_0 问题属性：经典场论中的常见问题，包括构建试探假设、计算张量缩并、求解张量方程等。 Mendeley Data的CPC仓库中收录的该程序版本：AESH_v1_0；xTras；DOI:10.1016/j.cpc.2014.02.006