Most Complex Regular Ideal Languages
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Date
2016-10-17
Authors
Liu, Bo Yang Victor
Davies, Sylvie
Brzozowski, Janusz
Advisor
Journal Title
Journal ISSN
Volume Title
Publisher
Discrete Mathematics and Theoretical Computer Science
Abstract
A right ideal (left ideal, two-sided ideal) is a non-empty language $L$ over an alphabet $\Sigma$ such that $L=L\Sigma^*$ ($L=\Sigma^*L$, $L=\Sigma^*L\Sigma^*$). Let $k=3$ for right ideals, 4 for left ideals and 5 for two-sided ideals. We show that there exist sequences ($L_n \mid n \ge k $) of right, left, and two-sided regular ideals, where $L_n$ has quotient complexity (state complexity) $n$, such that $L_n$ is most complex in its class under the following measures of complexity: the size of the syntactic semigroup, the quotient complexities of the left quotients of $L_n$, the number of atoms (intersections of complemented and uncomplemented left quotients), the quotient complexities of the atoms, and the quotient complexities of reversal, star, product (concatenation), and all binary boolean operations. In that sense, these ideals are "most complex" languages in their classes, or "universal witnesses" to the complexity of the various operations.
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Keywords
atom, basic operations, ideal, most complex, quotient, regular language, state complexity, syntactic semigroup, universal witness