Now showing items 1-7 of 7

    • Caterpillars in Erdős–Hajnal 

      Liebenau, Anita; Pilipczuk, Marcin; Seymour, Paul; Spirkl, Sophie (Elsevier, 2019-05)
      Let T be a tree such that all its vertices of degree more than two lie on one path; that is, T is a caterpillar subdivision. We prove that there exists ε > 0 such that for every graph G with |V(G)| ≥ 2 not containing T as ...
    • Complexity Dichotomy for List-5-Coloring with a Forbidden Induced Subgraph 

      Hajebi, Sepehr; Li, Yanjia; Spirkl, Sophie (Society for Industrial and Applied Mathematics, 2022-08-30)
      For a positive integer r and graphs G and H, we denote by G+H the disjoint union of G and H and by rH the union of r mutually disjoint copies of H. Also, we say G is H-free if H is not isomorphic to an induced subgraph of ...
    • Induced subgraphs of graphs with large chromatic number. VIII. Long odd holes 

      Chudnovsky, Maria; Scott, Alex; Seymour, Paul; Spirkl, Sophie (Elsevier, 2020-01)
      We prove a conjecture of András Gyárfás, that for all k, l, every graph with clique number at most κ and sufficiently large chromatic number has an odd hole of length at least ℓ.
    • Minimal induced subgraphs of two classes of 2-connected non-Hamiltonian graphs 

      Cheriyan, Joseph; Hajebi, Sepehr; Qu, Zishen; Spirkl, Sophie (Elsevier, 2022-07)
      In 1981, Duffus, Gould, and Jacobson showed that every connected graph either has a Hamiltonian path, or contains a claw (K1,3) or a net (a fixed six-vertex graph) as an induced subgraph. This implies that subject to being ...
    • A note on simplicial cliques 

      Chudnovsky, Maria; Scott, Alex; Seymour, Paul; Spirkl, Sophie (Elsevier, 2021-09)
      Motivated by an application in condensed matter physics and quantum information theory, we prove that every non-null even-hole-free claw-free graph has a simplicial clique, that is, a clique K such that for every vertex v ...
    • On coloring digraphs with forbidden induced subgraphs 

      Carbonero, Alvaro (University of Waterloo, 2023-04-25)
      This thesis mainly focuses on the structural properties of digraphs with high dichromatic number. The dichromatic number of a digraph $D$, denoted by $\dichi(D)$, is designed to be the directed analog of the chromatic ...
    • Pure pairs. I. Trees and linear anticomplete pairs 

      Chudnovsky, Maria; Scott, Alex; Seymour, Paul; Spirkl, Sophie (Elsevier, 2020-12-02)
      The Erdős-Hajnal conjecture asserts that for every graph H there is a constant c > 0 such that every graph G that does not contain H as an induced subgraph has a clique or stable set of cardinality at least |G|c. In this ...

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