Evènement pour le groupe Séminaire Méthodes Formelles

Date 2017-02-14  11:00-12:00
TitreEmptiness of nonzero automata is decidable 
RésuméZero automata are a probabilistic extension of parity automata on infinite trees. Bojanczyk has shown recently that the satisfiability of a certain probabilistic variant of MSO, called TMSO+zero reduces to the emptiness problem for zero automata. These automata perform random walks on the input (binary) tree: when the automaton is in a state q on a node labelled with a, it selects non-deterministically a transition (q,a,r_0,r_1) and moves with equal probability 1/2 either to the left node in state r_0 or to the right node in state r_1.. The acceptance condition of zero automata impose conditions not only on the parity of individual branches of the run but as well on some other properties of runs that should occur almost-surely or with positive probability. We introduce a variant of zero automata called nonzero automata and we show that i) for every zero automaton there is an equivalent nonzero automaton of quadratic size ii) the emptiness problem of nonzero automata is decidable, with complexity {sc np}. These results imply that TMSO+zero has decidable satisfiability. Joint work with Mikolaj Danger Bojanczyk and Edon Kelmendi 
OrateurHugo Gimbert 

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