Fall 2016

Fellows Logic Open Seminar

Dec 12, 2016 2:00 pm – 3:30 pm 

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Calvin Lab Rm 116

On Recognizable Languages of Graphs

We prove a conjecture of Courcelle, which states that a graph property is definable in MSO with modular counting predicates on graphs of constant treewidth if, and only if it is recognizable in the following sense: constant-width tree decompositions of graphs satisfying the property can be recognized by tree automata. While the forward implication is a classic fact known as Courcelle's theorem, the converse direction remained open.
Joint work with Michał Pilipczuk