English

Simplicial generation of Chow rings of matroids

Combinatorics 2025-03-18 v6 Commutative Algebra Algebraic Geometry

Abstract

We introduce a presentation of the Chow ring of a matroid by a new set of generators, called "simplicial generators." These generators are analogous to nef divisors on projective toric varieties, and admit a combinatorial interpretation via the theory of matroid quotients. Using this combinatorial interpretation, we (i) produce a bijection between a monomial basis of the Chow ring and a relative generalization of Schubert matroids, (ii) recover the Poincar\'e duality property, (iii) give a formula for the volume polynomial, which we show is log-concave in the positive orthant, and (iv) recover the validity of Hodge-Riemann relations in degree 1, which is the part of the Hodge theory of matroids that currently accounts for all combinatorial applications of [AHK18]. Our work avoids the use of "flips," the key technical tool employed in [AHK18].

Keywords

Cite

@article{arxiv.1905.07114,
  title  = {Simplicial generation of Chow rings of matroids},
  author = {Spencer Backman and Christopher Eur and Connor Simpson},
  journal= {arXiv preprint arXiv:1905.07114},
  year   = {2025}
}

Comments

37 pages; v2-v4: minor revisions, v4 to appear in JEMS. v6: revised a local error in Proposition 5.2.3