English

Matroid Chern-Schwartz-MacPherson cycles and Tutte activities

Combinatorics 2022-07-21 v2

Abstract

Lop\'ez de Medrano-Rin\'con-Shaw defined Chern-Schwartz-MacPherson cycles for an arbitrary matroid MM and proved by an inductive geometric argument that the unsigned degrees of these cycles agree with the coefficients of T(M;x,0)T(M;x,0), where T(M;x,y)T(M;x,y) is the Tutte polynomial associated to MM. Ardila-Denham-Huh recently utilized this interpretation of these coefficients in order to demonstrate their log-concavity. In this note we provide a direct calculation of the degree of a matroid Chern-Schwartz-MacPherson cycle by taking its stable intersection with a generic tropical linear space of the appropriate codimension and showing that the weighted point count agrees with the Gioan-Las Vergnas refined activities expansion of the Tutte polynomial.

Keywords

Cite

@article{arxiv.2007.10278,
  title  = {Matroid Chern-Schwartz-MacPherson cycles and Tutte activities},
  author = {Ahmed Umer Ashraf and Spencer Backman},
  journal= {arXiv preprint arXiv:2007.10278},
  year   = {2022}
}
R2 v1 2026-06-23T17:15:18.138Z