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Deciding the Borel complexity of regular tree languages (1403.3502v1)
Published 14 Mar 2014 in cs.LO, cs.FL, and math.LO
Abstract: We show that it is decidable whether a given a regular tree language belongs to the class ${\bf \Delta0_2}$ of the Borel hierarchy, or equivalently whether the Wadge degree of a regular tree language is countable.