Formal languages
The method of forced enumeration for nondeterministic automata
Acta Informatica
Nondeterministic space is closed under complementation
SIAM Journal on Computing
Computability, complexity, and languages (2nd ed.): fundamentals of theoretical computer science
Computability, complexity, and languages (2nd ed.): fundamentals of theoretical computer science
Introduction to the Theory of Computation
Introduction to the Theory of Computation
Topological Aspects of Regular Languages
Topological Aspects of Regular Languages
Algorithm Design
A note on the space complexity of some decision problems for finite automata
Information Processing Letters
Relationships between nondeterministic and deterministic tape complexities
Journal of Computer and System Sciences
Space-bounded reducibility among combinatorial problems
Journal of Computer and System Sciences
| Hi-index | 5.23 |
We study the Boolean algebras R,CS,D of regular languages, context-sensitive languages and decidable languages, respectively, over any alphabet. It is well known that R@?CS@?D, with proper inclusions. After observing that these Boolean algebras are all isomorphic, we study some immunity properties: for instance we prove that for every coinfinite decidable language L there exists a decidable language L^' such that L@?L^', L^'-L is infinite, and there is no context-sensitive language L^'', with L^''@?L^' unless L^''-L is finite; similarly, for every coinfinite regular language L there exists a context-sensitive language L^' such that L@?L^', L^'-L is infinite, and there is no regular language L^'' such that L^''@?L^', unless L^''-L is finite.