The degree-sequence conjecture for perfect clique packings

Let n,rNn,r\in\mathbb N with rr dividing nn. Let GG be a graph on nn vertices with degree sequence d1dnd_1\leq\dots\leq d_n. A perfect KrK_r-packing is a collection of vertex-disjoint copies of KrK_r covering all vertices of GG.

Degree-sequence conjecture. If

di(r2)n/r+ifor all i<n/r,d_i\geq (r-2)n/r+i\quad\text{for all }i<n/r,

and

dn/r+1(r1)n/r,d_{n/r+1}\geq (r-1)n/r,

then GG contains a perfect KrK_r-packing.

This extends the Hajnal–Szemerédi theorem because the condition permits n/rn/r vertices to have degree below (r1)n/r(r-1)n/r. The degree condition is essentially best possible, and the conjecture is proved when GG is additionally Kr+1K_{r+1}-free; the general case remains open.

Sources & referencesView supporting material

Primary source

József Balogh, Alexandr V. Kostochka and Andrew Treglown, “On perfect packings in dense graphs”, arXiv:1110.3490 (2013).

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