Problems

Around the Kemeny median problem, which stays open for m=3 and m=5 voters, the paper refutes three conjectures on tournament inducibility: both conjectures of Milosz, Hamel and Pierrot (the 3-cycle extension for odd m≥5, and FAS=HS_3 at…

Is the chromatic symmetric function X_G Schur positive for every claw-free graph G? Two explicit 12-vertex line graphs have Schur coefficients -64 and -40 at s_(3,3,3,3).

A Cayley graph is minimal when no proper subset of its connection set generates the group. Babai asked whether minimal Cayley graphs have bounded chromatic number. Resolved negatively: finite minimal Cayley graphs exist with arbitrarily…

For every connected graph, is the variance of its positive adjacency eigenvalues at most its order divided by its average distance? Exact dumbbell-graph certificates refute the bound under both conventions for average distance.

For a differential poset P, must the weighted 2-multichain series M_P,2(q) be a rational multiple of F_P(q)^2, the square of its rank generating series?

Is the zero forcing number of every connected graph with maximum degree 3 at most its independence number plus one? A connected 24-vertex subcubic graph with independence number 9 and zero forcing number 11 refutes this 2017 TxGraffiti…

Erdős asked whether every n-point set in Euclidean space whose pairwise distances are mutually at least 1 apart must have diameter at least (1+o(1))n^2. Disproved: an explicit high-dimensional construction beats the conjectured constant.

If G is connected, cubic and diamond-free, must the zero-forcing number satisfy Z(G) ≤ γ(G) + 2? A connected cubic triangle-free 14-vertex graph has Z = 7 and γ = 4.

Must every r-differential poset have at least as many elements in each rank as Y^r, the r-th Cartesian power of Young's lattice? For r = 3 the new construction has fourth-rank size 50 against 51 for Y^3.