Recognition of Seifert fibered spaces with boundary is in NP

Abstract

AbstractWe show that the decision problem of recognising whether a triangulated 3-manifold admits a Seifert fibered structure with non-empty boundary is in NP. We also show that the problem of deciding whether a given triangulated Seifert fibered space with non-empty boundary admits certain Seifert data is in $${{{\textbf {NP}}}{}}\cap \text {co-}{} {\textbf {NP}}$$ NP ∩ co- NP . We do this by proving that in any triangulation of a Seifert fibered space with boundary there is both a fundamental horizontal surface of small degree and a complete collection of normal vertical annuli whose total weight is bounded by an exponential in the square of the triangulation size.