5 problems

Lieb–Seiringer conjecture. This coefficient is non-negative.

Collins–Dykema–Torres-Ayala conjecture. This coefficient is non-negative.

Let $C_n$ denote the $n\times n$ Chet matrix, and let $C=\{n:C_n\text{ is entry-wise nonnegative}\}$. Chet Conjecture. One has … More strongly, … The paper presents this as its mai…

Let $A$ be a minimally AP-irreducible sign pattern matrix of order $n$ whose diagonal entries are all zero. A sign pattern matrix $A$ is minimally AP-irreducible if it is AP-irredu…

Let $K\subseteq \mathbb R$ be either a union of an unbounded interval and a point, or a union of two unbounded intervals and a point. Suppose $S$ is the natural description of $K$.…