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Quasi-random Permutations Are Characterised by 4-Point Densities

Thu 28 February 2013, 16:30

Oleg Pikhurko
Warwick

Combinatorics

Organisers: Tom McCourt, Tony Nixon, Karen Gunderson

ABSTRACT
A sequence of permutations is called quasi-random if the
frequency of any k-term sub-permutation is 1/k!+o(1). By using the
analytic language of permutation limits developed by Hoppen et al, we
prove that it suffices to check k=4 only. This answers a question of
Ron Graham.

Joint work with Daniel Kral'