First-order spectra with one variable
Journal of Computer and System Sciences
A nontrivial lower bound for an NP problem on automata
SIAM Journal on Computing
Linear Time Algorithms and NP-Complete Problems
SIAM Journal on Computing
The quantifier structure of sentences that characterize nondeterministic time complexity
Computational Complexity
Invariance properties of RAMs and linear time
Computational Complexity
First-order spectra with one binary predicate
Theoretical Computer Science
Monadic logical definability of nondeterministic linear time
Computational Complexity
Computers and Intractability: A Guide to the Theory of NP-Completeness
Computers and Intractability: A Guide to the Theory of NP-Completeness
On Bijections vs. Unary Functions
STACS '96 Proceedings of the 13th Annual Symposium on Theoretical Aspects of Computer Science
A Conjunctive Logical Characterization of Nondeterministic Linear Time
CSL '97 Selected Papers from the11th International Workshop on Computer Science Logic
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Relational queries computable in polynomial time (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
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The aim of this paper is to give two new logical characterizations of NLIN (nondeterministic linear time) improving significantly a previous characterization of E. Grandjean (1994, SIAM J. Comput. 23, 573-597; and F. Olive, 1998, Comput. Complexity 7, 54-97). It is known that NLIN coincides with the class of problems definable by formulas of the prenex form f1... fk ψ where the fi are unary function symbols and ψ is first-order, prenex, with only one universal quantifier. We show that the characterization remains true in the two following cases: (a) Unary functions are replaced by a single binary relation whose outdegree is bounded by some fixed constant h. (b) When only ordered structures are considered, unary functions are restricted to be bijective.