Setting of this paper is Bishop's constructive mathematics. For a relation σ on a set with apartness is called quasi-antiorder if it is consistent and cotransitive. The quasi-antiorder σ is complete if holds . 0 1 / = σ σ − ∩ In this paper the following assertion ‘A quasi-antiorder is the intersection of a collection of quasi-antiorders.’ is given.

The set of synchronizing words a given n-state automaton forms regular language recognizable by an with \(2^n - n\) states. size recognizing for the is linked to computational problems related synchronization and length words. Hence, it natural investigate automata extremal this property, i.e., such that minimal deterministic has sync-maximal permutation groups have been introduced in [S. Hoffm...

Billey, Jockusch, and Stanley characterized 321-avoiding permutations by a property of their reduced decompositions. This paper generalizes that result with a detailed study of permutations via their reduced decompositions and the notion of pattern containment. These techniques are used to prove a new characterization of vexillary permutations in terms of their principal dual order ideals in a ...