Theory of recursive functions and effective computability
Theory of recursive functions and effective computability
Unrestricted complementation in language equations over a one-letter alphabet
Theoretical Computer Science
Maximal and minimal solutions to language equations
Journal of Computer and System Sciences
Context-free languages and pushdown automata
Handbook of formal languages, vol. 1
Two Families of Languages Related to ALGOL
Journal of the ACM (JACM)
Journal of Automata, Languages and Combinatorics - Special issue: selected papers of the second internaional workshop on Descriptional Complexity of Automata, Grammars and Related Structures (London, Ontario, Canada, July 27-29, 2000)
Theory of Automata
Conjunctive Grammars and Systems of Language Equations
Programming and Computing Software
Solution of parallel language equations for logic synthesis
Proceedings of the 2001 IEEE/ACM international conference on Computer-aided design
A Universal Turing Machine with 3 States and 9 Symbols
DLT '01 Revised Papers from the 5th International Conference on Developments in Language Theory
Nonterminal complexity of programmed grammars
Theoretical Computer Science
On the number of nonterminals in linear conjunctive grammars
Theoretical Computer Science
Information and Computation
Reversal-bounded multipushdown machines
Journal of Computer and System Sciences
Decision problems for language equations with Boolean operations
ICALP'03 Proceedings of the 30th international conference on Automata, languages and programming
The power of commuting with finite sets of words
STACS'05 Proceedings of the 22nd annual conference on Theoretical Aspects of Computer Science
On computational universality in language equations
MCU'04 Proceedings of the 4th international conference on Machines, Computations, and Universality
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It has recently been shown that several computational models, such as trellis automata, recursive functions and Turing machines, admit characterization by resolved systems of language equations with different sets of language-theoretic operations. This paper investigates how simple the systems of equations from the computationally universal types could be while still retaining their universality. It is proved that the universality and the associated hardness of decision problems begins at one-variable equations. Additionally, it is shown that language equations with added quotient with regular languages can specify every set representable in first-order Peano arithmetic.