Sivaraman's cop-number conjecture for path-free graphs

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Let PkP_k denote the path on kk vertices, let GG be a graph, and let c(G)c(G) denote its cop number. A graph is PkP_k-free if it contains no induced subgraph isomorphic to PkP_k. Sivaraman's conjecture. For all k≥5k\geq 5, if GG is PkP_k-free, then

c(G)≤k−3.c(G)\leq k-3.

The conjecture proposes an improvement over the known bound that every connected PkP_k-free graph is (k−2)(k-2)-cop win. Its general P5P_5 case was recently proved by Chudnovsky, Norin, Seymour, and Turcotte; the statement for general kk is therefore not uniformly open in the same form.

References

Primary source

Alexander Clow and Erin Meger, “Cops and Robbers on Graphs with Path Constraints”, arXiv:2509.10941 (2025).

Additional references

9 papers in this index state this conjecture (2019–2025). The statement above is taken from the most recent of them; the others are arXiv:2505.15416, arXiv:2504.04496, arXiv:2504.14863, arXiv:2302.06800, arXiv:2104.02807, arXiv:2001.03124, arXiv:1908.11478, arXiv:1903.11484.

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