The large-order extremal construction conjecture for subcube intersection graphs

Let CdC_d be the family of subcubes of {0,1}d\{0,1\}^d, and for a subcube xCdx\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 n2×2d/2+(r2)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)={xCd: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.

Sources & referencesView supporting material

Primary source

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

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