Embeddability in is NP-hard
arXiv:1708.07734
Abstract
We prove that the problem of deciding whether a 2- or 3-dimensional simplicial complex embeds into is NP-hard. Our construction also shows that deciding whether a 3-manifold with boundary tori admits an filling is NP-hard. The former stands in contrast with the lower dimensional cases which can be solved in linear time,and the latter with a variety of computational problems in 3-manifold topology (for example, unknot or 3-sphere recognition, which are in NP and co-NP assuming the Generalized Riemann Hypothesis). Our reduction encodes a satisfiability instance into the embeddability problem of a 3-manifold with boundary tori, and relies extensively on techniques from low-dimensional topology, most importantly Dehn fillings on link complements.