Generalized Grassmann invariant-redrawn
Abstract
This is my old unpublished paper called "The generalized Grassmann invariant". It shows how "pictures" also known as "Peiffer diagrams" represent elements of for any group and shows that is isomorphic to a group of deformation classes of pictures for the Steinberg group of . A picture representing an element of order in is also constructed. In this updated version of the paper, we modify only the pictures and leave the text more or less unchanged. We also added an Appendix to explain the new pictures using representations of quivers and root systems of type . Often, some roots are missing in the Morse pictures. We give two ideas to replace these roots. One uses "ghost handle slides" to obtain a standard picture. The second idea uses the (real) Cartan subalgebra to obtain a "relative" picture for a torsion class and adds "ghost modules" which are directly related to the generalized Grassmann invariant. Additions and changes are in blue except the pictures are black with colored ghosts.
Cite
@article{arxiv.2502.19147,
title = {Generalized Grassmann invariant-redrawn},
author = {Kiyoshi Igusa},
journal= {arXiv preprint arXiv:2502.19147},
year = {2025}
}
Comments
47 pages, 9 figures, v2: preview of more precise description of ghost modules added with reference