A simply connected universal fibration with unique path lifting over a Peano continuum with non-simply connected universal covering space

TL;DR

This paper constructs a 2D Peano continuum with a universal fibration having unique path lifting, a trivial fundamental group, and a non-simply connected universal cover, challenging classical covering space theory.

Contribution

It introduces a new example of a universal fibration over a Peano continuum with unusual properties, including a trivial fundamental group and no universal cover.

Findings

Existence of a universal fibration with trivial fundamental group

No universal covering projection exists for the constructed space

The universal object is not an inverse limit of coverings

Abstract

We present a 2-dimensional Peano continuum $\mathbb{T}\subseteq \mathbb{R}^3$ with the following properties: (1) There is a universal covering projection $q:\overline{\mathbb{T}}\rightarrow \mathbb{T}$ with uncountable fundamental group $\pi_1(\overline{\mathbb{T}})$; (2) For every $1\not=[\overline{\alpha}]\in \pi_1(\overline{\mathbb{T}},\ast)$, there is a covering projection $r:(E,e)\rightarrow (\overline{\mathbb{T}},\ast)$ such that $[\overline{\alpha}]\not\in r_\#\pi_1(E,e)$; (3) There is no universal covering projection $r:E\rightarrow \overline{\mathbb{T}}$; (4) The universal object $p:\widetilde{\mathbb{T}}\rightarrow \mathbb{T}$ in the category of fibrations with unique path lifting (and path-connected total space) over $\mathbb{T}$ has trivial fundamental group $\pi_1(\widetilde{\mathbb{T}})=1$; (5) $p:\widetilde{\mathbb{T}}\rightarrow \mathbb{T}$ is not a path component of an inverse limit of covering projections over $\mathbb{T}$.