Partitioning permutations into monotone subsequences
The electronic journal of combinatorics, Tome 28 (2021) no. 3
A permutation is $k$-coverable if it can be partitioned into $k$ monotone subsequences. Barber conjectured that, for any given permutation, if every subsequence of length ${k+2 \choose 2}$ is $k$-coverable then the permutation itself is $k$-coverable. This conjecture, if true, would be best possible. Our aim in this paper is to disprove this conjecture for all $k \geqslant 3$. In fact, we show that for any $k$ there are permutations such that every subsequence of length at most $(k/6)^{2.46}$ is $k$-coverable while the permutation itself is not.
@article{10_37236_10267,
author = {David W\"arn},
title = {Partitioning permutations into monotone subsequences},
journal = {The electronic journal of combinatorics},
year = {2021},
volume = {28},
number = {3},
doi = {10.37236/10267},
zbl = {1473.05015},
url = {http://geodesic.mathdoc.fr/articles/10.37236/10267/}
}
David Wärn. Partitioning permutations into monotone subsequences. The electronic journal of combinatorics, Tome 28 (2021) no. 3. doi: 10.37236/10267
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