Undecidability of the universal support problem for weighted automata over zero-sum-free commutative semirings
Manfred Droste, Werner Kuich · Theoretical Computer Science · 2024
We show that there is an effectively given zero-sum-free commutative semiring S, contained as the subsemiring of nonnegative elements in an effectively given commutative ordered ring, for which there are no procedures deciding, given a weighted finite automaton over S, whether its support is the language of all words or whether its support is infinite. In particular, by a result of D. Kirsten (2011), since S is zero-sum-free and commutative, the support is recognizable by a classical finite automaton, but such an automaton or even just a pushdown automaton for its support cannot be constructed effectively.