Fuentes–Kamat conjecture on Erdős–Ko–Rado subfamilies of perfect matchings

Let MnM_n be the graph with vertex set

V(Mn)={a1,a2,,an,b1,b2,,bn}V(M_n)=\{a_1, a_2, \dots, a_n, b_1, b_2,\dots, b_n\}

and edge set

E(Mn)={(a1,b1),(a2,b2),,(an,bn)}.E(M_n)=\{(a_1,b_1), (a_2,b_2), \dots, (a_n,b_n)\}.

Let H(p,s)(n)\mathcal{H}^{(p,s)}(n) be the family of subsets of V(Mn)V(M_n) that contain exactly 2p+s2p+s vertices and span exactly pp edges, equivalently, that contain pp disjoint edges and ss isolated vertices. For a family H\mathcal{H} and an element xx, write Hx={HH:xH}\mathcal{H}_x=\{H\in\mathcal{H}:x\in H\}; the family H\mathcal{H} is EKR if some xx satisfies FHx|\mathcal{F}|\leq|\mathcal{H}_x| for every intersecting subfamily FH\mathcal{F}\subseteq\mathcal{H}. Fuentes–Kamat conjecture. For non-negative integers p,sp,s satisfying 12p+sn1\leq 2p+s\leq n, H(p,s)(n)\mathcal{H}^{(p,s)}(n) is EKR. This conjecture concerns an Erdős–Ko–Rado property for subfamilies of subsets associated with a perfect matching; the source notes that Fuentes and Kamat had previously conjectured this statement and proved it for a certain range of parameters, while the general assertion is presented here as the conjectural claim.

Sources & referencesView supporting material

Primary source

Dániel T. Nagy, “An Erdős-Ko-Rado type theorem for subgraphs of perfect matchings”, arXiv:2407.17455 (2024).

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