Year: 2010
Type: preprint
Abstract: We prove the following theorem. Suppose that $M$ is a trim DFA on the Boolean alphabet $0,1$. The language $Ł(M)$ is well-ordered by the lexicographic order $\slex$ iff whenever the non sink states $q,q.0$ are in the same strong component, then $q.1$ is a sink. It is easy to see that this property is sufficient. In order to show the necessity, we analyze the behavior of a $\slex$-descending sequence of words. This property is used to obtain a polynomial time algorithm to determine, given a DFA $M$, whether $Ł(M)$ is well-ordered by the lexicographic order. Last, we apply an argument in \cite{BE,BEa} to give a proof that the least nonregular ordinal is $ω^ω$.
Source: arXiv (Cornell University)
Authors: Bloom, Stephen L., Zhang, YiDi
Institution: Stevens Institute of Technology
Language: English
Subfield: Computational Theory and Mathematics
Field: Computer Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2951597089