The Magic Number Problem for Subregular Language Families

Markus Holzer
Sebastian Jakobi
Martin Kutrib

We investigate the magic number problem, that is, the question whether there exists a minimal n-state nondeterministic finite automaton (NFA) whose equivalent minimal deterministic finite automaton (DFA) has alpha states, for all n and alpha satisfying n less or equal to alpha less or equal to exp(2,n). A number alpha not satisfying this condition is called a magic number (for n). It was shown in [11] that no magic numbers exist for general regular languages, while in [5] trivial and non-trivial magic numbers for unary regular languages were identified. We obtain similar results for automata accepting subregular languages like, for example, combinational languages, star-free, prefix-, suffix-, and infix-closed languages, and prefix-, suffix-, and infix-free languages, showing that there are only trivial magic numbers, when they exist. For finite languages we obtain some partial results showing that certain numbers are non-magic.

In Ian McQuillan and Giovanni Pighizzini: Proceedings Twelfth Annual Workshop on Descriptional Complexity of Formal Systems (DCFS 2010), Saskatoon, Canada, 8-10th August 2010, Electronic Proceedings in Theoretical Computer Science 31, pp. 110–119.
Published: 7th August 2010.

ArXived at: http://dx.doi.org/10.4204/EPTCS.31.13 bibtex PDF

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