David E Speyer

collaborators

5 papers

math.CO2026

L-log-concavity and a proof of the conjecture of Lam, Postnikov and Pylyavskyy

David E Speyer

Let $I^»$ , $I^¼$ , $I^»^{'}$ , $I^¼^{'}$ be partitions. The conjecture of Lam, Postnikov and Pylyavskyy states that, if $I^» + I^¼ = I^»^{'} + I^¼^{'}$ , and $\min(Î»_i-Î»_j, Î¼_i-Î¼_j) \leq Î»'_i - Î»'_j \…

math.CO2026

The omega invariant of a matroid

Alex Fink, Kris Shaw, David E Speyer

The third author introduced the $g$ -polynomial $g_{M} (t)$ of a matroid, a covaluative matroid statistic which is unchanged under series and parallel extension. The $g$ -polynomial of…

math.CO2025

Affine extended weak order is a lattice

Grant T. Barkley, David E Speyer

Coxeter groups are equipped with a partial order known as the weak order, such that $u \leq v$ if the inversions of $u$ are a subset of the inversions of $v$ . In finite Coxeter gro…

math.CO2025

Extended Weak Order for the Rank 3 Universal Coxeter Group

Grant Barkley, Colin Defant, Patricia Hersh +3

The weak order is a classical poset structure on a Coxeter group; it is a lattice when the group is finite but merely a meet-semilattice when the group is infinite. Motivated by pr…

math.CO2025

Rowmotion and Echelonmotion

Colin Defant, Yuhan Jiang, Rene Marczinzik +4

Given a linear extension $I ¨ $ of a finite poset $R$ , we consider the permutation matrix indexing the Schubert cell containing the Cartan matrix of $R$ with respect to $I ¨ $ . This yi…