
Abstract We consider the length of the longest word definable in FO and MSO via a formula of size n. For both logics we obtain as an upper bound for this number an exponential tower of height linear in n. We prove this by counting types with respect to a fixed quantifier rank. As lower bounds we obtain for both FO and MSO an exponential tower of height in the order of a rational power of n. We show these lower bounds by giving concrete formulas defining word representations of levels of the cumulative hierarchy of sets. In addition, we consider the Löwenheim-Skolem and Hanf numbers of these logics on words and obtain similar bounds for these as well.
FOS: Computer and information sciences, Computer Science - Logic in Computer Science, 213 Electronic, automation and communications engineering, electronics, monadic second-order logic, Model theory of finite structures, logic on words, succinctness, Mathematics - Logic, 111, 113, 004, Logic in Computer Science (cs.LO), Descriptive complexity and finite models, FOS: Mathematics, F.4.1, Logic (math.LO)
FOS: Computer and information sciences, Computer Science - Logic in Computer Science, 213 Electronic, automation and communications engineering, electronics, monadic second-order logic, Model theory of finite structures, logic on words, succinctness, Mathematics - Logic, 111, 113, 004, Logic in Computer Science (cs.LO), Descriptive complexity and finite models, FOS: Mathematics, F.4.1, Logic (math.LO)
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