Transport of patterns by Burge transpose

We take the first steps in developing a theory of transport of patterns from Fishburn permutations to (modified) ascent sequences. Given a set of pattern avoiding Fishburn permutations, we provide an explicit construction for the basis of the corresponding set of modified ascent sequences. Our approach is in fact more general and can transport patterns between permutations and equivalence classes of so called Cayley permutations. This transport of patterns relies on a simple operation we call the Burge transpose. It operates on certain biwords called Burge words. Moreover, using mesh patterns on Cayley permutations, we present an alternative view of the transport of patterns as a Wilf-equivalence between subsets of Cayley permutations. We also highlight a connection with primitive ascent sequences.Comment: 24 pages, 4 figure

Dynamical aspects of σ\sigma-machines

The $\sigma$-machine was recently introduced by Cerbai, Claesson and Ferrari as a tool to gain a better insight on the problem of sorting permutations with two stacks in series. It consists of two consecutive stacks, which are restricted in the sense that their content must at all times avoid a certain pattern: a given $\sigma$, in the first stack, and $21$, in the second. Here we prove that in most cases sortable permutations avoid a bivincular pattern $\xi$. We provide a geometric decomposition of $\xi$-avoiding permutations and use it to count them directly. Then we characterize the permutations with the property that the output of the $\sigma$-avoiding stack does not contain $\sigma$, which we call effective. For $\sigma=123$, we obtain an alternative method to enumerate sortable permutations. Finally, we classify $\sigma$-machines and determine the most challenging to be studied.Comment: 19 pages, 4 figures, 3 tables. arXiv admin note: text overlap with arXiv:2210.0362

Sorting permutations with pattern-avoiding machines

In this work of thesis we introduce and study a new family of sorting devices, which we call pattern-avoiding machines. They consist of two stacks in series, equipped with a greedy procedure. On both stacks we impose a static constraint in terms of pattern containment: reading the content from top to bottom, the first stack is not allowed to contain occurrences of a given pattern $\sigma$, whereas the second one is not allowed to contain occurrences of $21$. By analyzing the behavior of pattern-avoiding machines, we aim to gain a better understanding of the problem of sorting permutations with two consecutive stacks, which is currently one of the most challenging open problems in combinatorics.Comment: PhD Thesis, 137 page

Pattern-avoiding modified ascent sequences

We initiate an in-depth study of pattern avoidance on modified ascent sequences. Our main technique consists in using Stanley's standardization to obtain a transport theorem between primitive modified ascent sequences and permutations avoiding a bivincular pattern of length three. We enumerate some patterns via bijections with other combinatorial structures such as Fishburn permutations, lattice paths and set partitions. We settle the last remaining case of a conjecture by Duncan and Steingr\'imsson by proving that modified ascent sequences avoiding 2321 are counted by the Bell numbers.Comment: 32 pages, 4 figures, 2 table

Permutation patterns in genome rearrangement problems

In the context of the genome rearrangement problem, we analyze two well known models, namely the block transposition and the prefix block transposition models, by exploiting the connection with the notion of permutation pattern. More specifically, for any $k$, we provide a characterization of the set of permutations having distance $\leq k$ from the identity (which is known to be a permutation class) in terms of what we call generating permutations and we describe some properties of its basis, which allow to compute such a basis for small values of $k$.Comment: 8 pages. In: L. Ferrari, M. Vamvakari (eds.): Proceedings of the GASCom 2018 Workshop, Athens, Greece, 18--20 June 2018, published at http://ceur-ws.or