Handbook of formal languages, vol. 1
On Fatou properties of rational languages
Where mathematics, computer science, linguistics and biology meet
Automata, Languages, and Machines
Automata, Languages, and Machines
On the Decomposition of Finite Languages
On the Decomposition of Finite Languages
The Commutation of Finite Sets: a Challenging Problem
The Commutation of Finite Sets: a Challenging Problem
The Branching Point Approach to Conway's Problem
Formal and Natural Computing - Essays Dedicated to Grzegorz Rozenberg [on occasion of his 60th birthday, March 14, 2002]
The Commutation with Codes and Ternary Sets of Words
STACS '03 Proceedings of the 20th Annual Symposium on Theoretical Aspects of Computer Science
FCT '01 Proceedings of the 13th International Symposium on Fundamentals of Computation Theory
The branching point approach to Conway's problem
Formal and natural computing
A simple undecidable problem: the inclusion problem for finite substitutions on ab*c
Information and Computation
On the complexity of decidable cases of the commutation problem of languages
Theoretical Computer Science
Theoretical Computer Science - The art of theory
Regular solutions of language inequalities and well quasi-orders
Theoretical Computer Science - Automata, languages and programming: Algorithms and complexity (ICALP-A 2004)
Unresolved systems of language equations: expressive power and decision problems
Theoretical Computer Science
Theoretical Computer Science
Decision problems for language equations
Journal of Computer and System Sciences
The power of commuting with finite sets of words
STACS'05 Proceedings of the 22nd annual conference on Theoretical Aspects of Computer Science
Finite sets of words and computing
MCU'04 Proceedings of the 4th international conference on Machines, Computations, and Universality
On computational universality in language equations
MCU'04 Proceedings of the 4th international conference on Machines, Computations, and Universality
| Hi-index | 5.23 |
We prove two results on commutation of languages. First, we show that the maximal language commuting with a three-element language, i.e. its centralizer, is rational, thus giving an affirmative answer to a special case of a problem proposed by Conway in 1971. Second, we characterize all languages commuting with a three-element code. The characterization is similar to the one proved by Bergman for polynomials over noncommuting variables (see Trans. Am. Math. Soc. 137 (1969) 327 and Algebraic Combinatorics on Words, Cambridge University Press, Cambridge, 2000): A language commutes with a three-element code X if and only if it is a union of powers of X.