3 problems

Ferroni–Fink's direct-sum conjecture. The direct sum $M_1\oplus M_2$ is extremal.

Let $M$ and $M'$ be matroids, and let $\varphi:M\to M'$ be a morphism in the category $\mathcal{M}$. Let $P_M(t)$ and $P_{M'}(t)$ denote their Kazhdan–Lusztig polynomials, and let…

Let $\operatorname{PolyMat}$ be the vector space of polymatroids, let $\operatorname{QSym}$ be the quasi-symmetric-function space, and let…