The large-order extremal construction conjecture for subcube intersection graphs

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Let CdC_d be the family of subcubes of {0,1}d\{0,1\}^d, and for a subcube x∈Cdx\in C_d let F(x)⊆[d]F(x)\subseteq[d] denote its fixed-coordinate set. Let I(n,d)\mathcal{I}(n,d) be the family of intersection graphs of nn subcubes in CdC_d, and let Kr+1K_{r+1} denote the complete graph on r+1r+1 vertices.

Large-order extremal construction conjecture. For any n≥2×2d/2+(r−2)n\geq 2\times2^{d/2}+(r-2), the maximum number of edges in a Kr+1K_{r+1}-free graph in I(n,d)\mathcal{I}(n,d) is attained by a graph GG which is a subgraph of a graph HH with

V(H)={x∈Cd:F(x)=Ri},V(H)=\{x\in C_d:F(x)=R_i\},

where, if Pi=[d]∖RiP_i=[d]\setminus R_i, then P1,…,PkP_1,\dots,P_k is a partition of [d][d] for some kk, and Pk+1,…,Pr=[d]P_{k+1},\dots,P_r=[d].

This complements the proposed small-order construction by allowing fewer than rr nontrivial classes and additional classes based on the full fixed-coordinate set. The paper motivates the construction through lower bounds for large nn but does not establish its optimality.

References

Primary source

J. Robert Johnson and Klas Markström, “Turán and Ramsey Properties of Subcube Intersection Graphs”, arXiv:1110.4283 (2011).

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