Local Permutation Removal;

Series
Combinatorics Seminar
Time
Friday, November 14, 2025 - 3:15pm for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Ruilin Shi – Duke University – ruilin.shi@duke.edu
Organizer
Tom Kelly

The permutation removal lemma was first proved by Klimosová and Král’, and later reproved by Fox and Wei in the context of permutation property testing. In this talk, we study a local version of the permutation removal problem. We show that for any permutation σ not equal to 12, 21, 132, 231, 213, or 312, there exists ε(σ) > 0 such that for any sufficiently large integer N, there is a permutation π of length N that is ε-far from being σ-free with respect to the ρ∞ distance, yet contains only a single copy of σ. Here, the ρ∞ distance is defined as an L∞-variant of the Earth Mover’s Distance between two permutations. We will also discuss our result on the local induced graph removal problem. This is joint work with Fan Wei.