From 0a1d404426cc8b9378cedd854864a9499c4c910e Mon Sep 17 00:00:00 2001 From: marcbezem Date: Thu, 15 Aug 2024 12:14:57 +0200 Subject: [PATCH] wip 4.6 --- group.tex | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/group.tex b/group.tex index 10cd899..04f5440 100644 --- a/group.tex +++ b/group.tex @@ -1958,20 +1958,23 @@ \section{The sign homomorphism} (and thus the sign) is preserved, as seen in~\cref{fig:permutation-crossings-isotopy}. \end{remark} -\section{\texorpdfstring{\inftygps}{∞-groups}} +\section{Infinity groups (\texorpdfstring{\inftygps}{∞-groups})} \label{sec:inftygps} -Disregarding the set-condition we get the simpler notion of \inftygps: +Disregarding the requirement that the classifying type +of a group $G$ is a groupoid (so that $\USym G$ is a set) +we get the simpler notion of \inftygps: \begin{definition}\label{def:inftygps} The type of $\infty$-groups is \[ \typeinftygp\defequi \Copy(\UUpconn), \quad\text{where}\quad - \UUpconn\defeq \sum_{A:\UU}\sum_{a:A} \isconn(A) + \UUpconn\defeq \sum_{A:\UU} A\times \isconn(A) \] is the type of pointed, connected types. - As for groups, we have the constructor $\mkgroup : \UUpconn \to \typeinftygp$ + As for groups, we have the constructor + $\mkgroup : \UUpconn \to \typeinftygp$ and the destructor $\clf : \typeinftygp \to \UUpconn$. \end{definition} @@ -2010,8 +2013,8 @@ \section{\texorpdfstring{\inftygps}{∞-groups}} Then $\conncomp\UU S$ is a groupoid, and the automorphism $\infty$-group $\Aut_\UU(S)$ is an ordinary group. - Because we have an embedding $\UUp^{=1} \hookrightarrow \UUp^{>0}$, - we get a corresponding embedding $\Group \hookrightarrow \typeinftygp$. + Because we have an inclusion $\UUp^{=1} \hookrightarrow \UUp^{>0}$, + we get a corresponding inclusion $\Group \hookrightarrow \typeinftygp$. \end{remark} \begin{definition}