Borodin-Kostochka Conjecture for a Family of P6-free Graphs
摘要
Borodin and Kostochka conjectured that every graph G with Δ ≥ 9 satisfies χ ≤ max {ω, Δ − 1}. Gupta and Pradhan proved the Borodin-Kostochka conjecture for (P5, C4)-free graphs. In this paper, we prove the Borodin-Kostochka conjecture for (P6, apple, torch)-free graphs, that is, graphs with no induced P6, no induced C5 with a hanging edge, and no induced C5 and C4 sharing exactly an induced P3. This generalizes the result of Gupta and Pradhan from the perspective of allowing the existence of P5.