Ideal decompositions and computation of tensor normal forms
摘要
Symmetry properties of r-times covariant tensors T can be described by certain linear subspaces W of the group ring K[S_r] of a symmetric group S_r. If for a class of tensors T such a W is known, the elements of the orthogonal subspace W^{\bot} of W within the dual space of K[S_r] yield linear identities needed for a treatment of the term combination problem for the coordinates of the T. We give the structure of these W for every situation which appears in symbolic tensor calculations by computer. Characterizing idempotents of such W can be determined by means of an ideal decomposition algorithm which works in every semisimple ring up to an isomorphism. Furthermore, we use tools such as the Littlewood-Richardson rule, plethysms and discrete Fourier transforms for S_r to increase the efficience of calculations. All described methods were implemented in a Mathematica package called PERMS.
引用
@article{arxiv.math/0211156,
title = {Ideal decompositions and computation of tensor normal forms},
author = {B. Fiedler},
journal= {arXiv preprint arXiv:math/0211156},
year = {2007}
}
备注
16 pages