Flavio D’Alessandro

Strongly transitive automata and the Černý conjecture

The synchronization problem is investigated for a new class of deterministic automata called strongly transitive. An extension to unambiguous automata is also considered.

On Finite-Index Indexed Grammars and Their Restrictions

The family, \({\mathsf{{\mathcal {L}}(IND_{LIN})}}\), of languages generated by linear indexed grammars has been studied in the literature. It is known that the Parikh image of every language in \({\mathsf{{\mathcal {L}}(IND_{LIN})}}\) is semi-linear. However, there are bounded semi-linear languages that are not in \({\mathsf{{\mathcal {L}}(IND_{LIN})}}\). Here, we look at larger families of (restricted) indexed languages and study their properties, their relationships, and their decidability properties.

Avoidable sets and well quasi-orders

Let I be a finite set of words and

Quantum Finite Automata and Linear Context-Free Languages: A Decidable Problem

\Rightarrow_{I}^{*}

Regularity of languages defined by formal series with isolated cut point

be the derivation relation generated by the set of productions {e → u | u ∈ I }. Let LIe be the set of words u such that

On the Commutative Equivalence of Context-Free Languages

\epsilon {\Rightarrow_{I}^{*}}

Homing vector automata

. We prove that the set I is unavoidable if and only if the relation

Teoria dei Semigruppi

\Rightarrow_{I}^{*}

Equivalenza di automi

is a well quasi-order on the set LIe. This result generalizes a theorem of [7]. Further generalizations are investigated.

Espressioni razionali e Star-height

We consider the so-called measure once finite quantum automata model introduced by Moore and Crutchfield in 2000. We show that given a language recognized by such a device and a linear context-free language, it is recursively decidable whether or not they have a nonempty intersection. This extends a result of Blondel et al. which can be interpreted as solving the problem with the free monoid in place of the family of linear context-free languages.