On Degree Sequences Forcing The Square of a Hamilton Cycle

A famous conjecture of Pósa from 1962 asserts that every graph on n vertices and with minimum degree at least 2n/3 contains the square of a Hamilton cycle. The conjecture was proven for large graphs in 1996 by Komlós, Sárközy and Szemerédi [23]. In this paper we prove a degree sequence version of Pósa’s conjecture: Given any η > 0, every graph G of sufficiently large order n contains the square of a Hamilton cycle if its degree sequence d1 ≤ · · · ≤ dn satisfies di ≥ (1/3 + η)n + i for all i ≤ n/3. The degree sequence condition here is asymptotically best possible. Our approach uses a hybrid of the Regularity-Blow-up method and the ConnectingAbsorbing method.