Slice closures of indexed languages and word equations with counting constraints
Laura Ciobanu, Georg Zetzsche · 2024
Indexed languages are a classical notion in formal language theory. As the language equivalent of second-order pushdown automata, they have received considerable attention in higher-order model checking. Unfortunately, counting properties are notoriously difficult to decide for indexed languages: So far, all results about non-regular counting properties show undecidability.