Almost-quasifibrations and fundamental groups of orbit configuration spaces

TL;DR

This paper introduces the concept of k-almost-quasifibrations, explores their properties, and applies these ideas to analyze the fundamental groups of orbit configuration spaces, supporting the Asphericity conjecture and revealing structural properties.

Contribution

It defines k-almost-quasifibrations, provides numerous examples, and applies these to determine the torsion-free and poly-free nature of fundamental groups of orbit configuration spaces.

Findings

Fundamental groups are torsion free for certain orbit configuration spaces.

Spaces with punctured 2-manifolds are poly-free, generalizing previous results.

Many examples of k-almost-quasifibrations are not quasifibrations.

Abstract

In this article we introduce the notion of a k-almost-quasifibration and give many examples. We also show that a large class of these examples are not quasifibrations. As a consequence, supporting the Asphericity conjecture of [19], we deduce that the fundamental group of the orbit configuration space of an effective and properly discontinuous action of a discrete group, on an aspherical 2-manifold with isolated fixed points is torsion free. Furthermore, if the 2-manifold has at least one puncture then it is poly-free, and hence has an iterated semi-direct product of free groups structure, which generalizes a result of Xicotencatl ([27], Theorem 6.3).