Problems
Everything in the archive: the problem as it was posed, what has been attempted against it, and who checked each attempt. The mark down the left of the list says who has looked — a person, a machine, or nobody yet. Human reviews and machine checks are counted separately and are never added together.
11 problems
VibeMathed records no statement for this problem. See erdosproblems.com for the original.
Must every connected graph satisfy the proposed upper bound on its independence number in terms of residue and largest induced-bipartite-subgraph order? The family overlineK_2r+1 ∨ (K_r sqcup K_r) violates it for every r ≥ 3.
Chromatic quasisymmetric functions of natural unit interval graphs were conjectured to have log-concave coefficients in the elementary basis. A connected 13-vertex example refutes it: for the Hessenberg function…
Simon conjectured that every skeleton of a simplex is extendably shellable. False: for every d ≥ 3 there is a pure d-dimensional shellable simplicial complex that is not shelling completable.
The target-free clique conjecture asserts that the supports of stable fixed points of a nondegenerate combinatorial threshold-linear network are exactly its target-free cliques, the bidirected cliques no outside vertex receives an edge…
VibeMathed records no statement for this problem. See erdosproblems.com for the original.
For every connected graph G, is α(G) ≤ ⌊ b(G) - log(ecc_avg(G)) ⌋, where b(G) is the largest induced-bipartite-subgraph order? An 11-vertex counterexample - a triangle with four leaves on each of two vertices - has α = 9 against bound 8.
Albertson and Berman conjectured that for every simple planar graph G on n vertices, the largest vertex set inducing a forest has size at least n/2. The standing lower bound since the same year has been Borodin's 2n/5, from his acyclic…
Jaeger conjectured that every bridgeless cubic graph G admits a Petersen coloring: a map φcolon E(G)→ E(P) into the edges of the Petersen graph P such that, for every vertex v of G, the three edges at v are sent to three edges meeting at a…
Teschner conjectured that every finite simple graph G with at least one edge satisfies b(G) ≤ 3/2Δ(G), where b(G) is the bondage number and Δ(G) is the maximum degree. Yavari gives a connected cubic bipartite graph on 18 vertices with…
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.