Complexity of controlled bad sequences over finite sets of $\mathbb{N}^d$

TL;DR

This paper establishes tight upper and lower bounds on the length of controlled bad sequences over finite sets of , linking these bounds to fast-growing complexity classes and automata emptiness problems.

Contribution

It provides the first tight bounds for controlled bad sequences over the majoring ordering, solving an open problem and connecting sequence length bounds to automata theory.

Findings

Bounds are tight for the majoring ordering.

Sequences are bounded by functions from the Cichon hierarchy.

Results lead to upper bounds for automata emptiness problems.

Abstract

We provide upper and lower bounds for the length of controlled bad sequences over the majoring and the minoring orderings of finite sets of $\mathbb{N}^d$. The results are obtained by bounding the length of such sequences by functions from the Cichon hierarchy. This allows us to translate these results to bounds over the fast-growing complexity classes. The obtained bounds are proven to be tight for the majoring ordering, which solves a problem left open by Abriola, Figueira and Senno (Theor. Comp. Sci, Vol. 603). Finally, we use the results on controlled bad sequences to prove upper bounds for the emptiness problem of some classes of automata.