12 results
Mikołaj Bojańczyk ; Bartek Klin.
$\omega$-clones are multi-sorted structures that naturally emerge as algebras for infinite trees, just as $\omega$-semigroups are convenient algebras for infinite words. In the algebraic theory of languages, one hopes that a language is regular if and only if it is recognized by an algebra that is […]
Published on November 29, 2019
Mikołaj Bojańczyk ; Laure Daviaud ; Bruno Guillon ; Vincent Penelle ; A. V. Sreejith.
We prove the undecidability of MSO on $\omega$-words extended with the second-order predicate $U_1(X)$ which says that the distance between consecutive positions in a set $X \subseteq \mathbb{N}$ is unbounded. This is achieved by showing that adding $U_1$ to MSO gives a logic with the same […]
Published on February 11, 2020