English

Hardness of almost embedding simplicial complexes in $\mathbb{R}^d$, II

Geometric Topology 2022-06-28 v1 Computational Complexity Computational Geometry Combinatorics

Abstract

A map f:KRdf: K \to \mathbb{R}^d of a simplicial complex is an almost embedding if f(σ)f(τ)=f(\sigma) \cap f(\tau) = \varnothing whenever σ,τ\sigma, \tau are disjoint simplices of KK. Fix integers d,k2d,k \geqslant 2 such that k+2d3k2+1k+2 \leqslant d \leqslant\frac{3k}2+1. Assuming that the "preimage of a cycle is a cycle" we prove NP\mathbf{NP}-hardness of the algorithmic problem of recognition of almost embeddability of finite kk-dimensional complexes in Rd\mathbb{R}^d. Assuming that PNP\mathbf{P} \ne \mathbf{NP} (and that the "preimage of a cycle is a cycle") we prove that the embedding obstruction is incomplete for kk-dimensional complexes in Rd\mathbb{R}^d using configuration spaces. Our proof generalizes the Skopenkov-Tancer proof of this result for d=3k2+1d = \frac{3k}{2} + 1.

Keywords

Cite

@article{arxiv.2206.13486,
  title  = {Hardness of almost embedding simplicial complexes in $\mathbb{R}^d$, II},
  author = {Emil Alkin},
  journal= {arXiv preprint arXiv:2206.13486},
  year   = {2022}
}

Comments

6 pages

R2 v1 2026-06-24T12:05:44.375Z