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Regular tree languages in low levels of the Wadge Hierarchy

Mikołaj Bojańczyk ; Filippo Cavallari ; Thomas Place ; Michał Skrzypczak.
In this article we provide effective characterisations of regular languages of infinite trees that belong to the low levels of the Wadge hierarchy. More precisely we prove decidability for each of the finite levels of the hierarchy; for the class of the Boolean combinations of open sets […]
Published on September 4, 2019

Optimizing tree decompositions in MSO

Mikołaj Bojańczyk ; Michał Pilipczuk.
The classic algorithm of Bodlaender and Kloks [J. Algorithms, 1996] solves the following problem in linear fixed-parameter time: given a tree decomposition of a graph of (possibly suboptimal) width k, compute an optimum-width tree decomposition of the graph. In this work, we prove that this problem […]
Published on February 3, 2022