The Ramsey number is the minimum n such that every red-blue colouring of the edges of the complete graph on n vertices contains a monochromatic copy of . It has been known since the work of Erdős and Szekeres in 1935, and Erdős in 1947, that , but in the …
Recently, Letzter proved that any graph of order n contains a collection P of paths with the following property: for all distinct edges e and f there exists a path in P which contains e but not f. We improve this upper bound to 19n, thus answering a question of Katona and confirming …
We study the fundamental problem of finding small dense subgraphs in a given graph. For a real number , we prove that every graph on vertices with average degree at least contains a subgraph of average degree at least on at most vertices. This is optimal up to the polylogarithmic …
The Erdős-Sós conjecture states that the maximum number of edges in an -vertex graph without a given -vertex tree is at most . Despite significant interest, the conjecture remains unsolved. Recently, Caro, Patkós, and Tuza considered this problem for host graphs that are connected. Settling a problem posed by them, for a -vertex tree …