Pure braid generators with vertical strands

Question

I've been using the braids package (https://www.ctan.org/pkg/braids) to draw braids. In general, it works fine for me, but when it comes to braid combing and other uses of pure braids, I would like to keep all strands but one vertical. For example, I would like to draw somehing like this:

The style of the braid package is elegant, but all I can do is this

which is not as clear.

This is my code

\documentclass{article}
\usepackage{braids}
\begin{document}
\begin{center}
\begin{tikzpicture}
\braid[ number of strands=12, 
 border height=2pt,
       style strands={2}{draw=none}, style strands={3}{draw=none}, style strands={8}{line width=2pt},style strands={10}{draw=none},style strands={11}{draw=none}] (braid) at (1,0), it's a name
          a_7 a_6 a_5 a_5 a_6^{-1} a_7^{-1};
\fill[ black ] ( 2 , -3 ) circle (2 pt ) ;
\fill[ black ] ( 3 , -3 ) circle (2 pt ) ;
\fill[ black ] ( 10 , -3 ) circle (2 pt ) ;
\fill[ black ] ( 11 , -3 ) circle (2 pt ) ;
\node[ at=(braid-5-s),  pin=north : $z_i$ ] {} ;
\node[ at=(braid-8-s),  pin=north : $z_j$ ] {} ;
\end{tikzpicture}
\end{center}
\end{document}

By the way, I would like to know if I can avoid those vertical lines beneath $z_i$ and $z_j$ using something instead of pin.

Answer 1

I'd like to argue that it is not very difficult to draw such things using elementary TikZ commands.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.shapes}
\begin{document}
% from https://tex.stackexchange.com/a/52849/121799
\tikzset{decorate sep/.style 2 args=
{decorate,decoration={shape backgrounds,shape=circle,shape size=#1,shape sep=#2}}}
\begin{tikzpicture}
\draw[white,double=black,very thick,-] (-3,-2) -- (-3,0);
\draw[smooth,white,double=black,line width=1mm,-] plot[variable=\x,domain=-2:2] ({-3.5*exp(-1.4*\x*\x)},{\x});
\node[anchor=south] at (0,2.1) {$z_j^0$};
\foreach \x in {-7,-4,-2,-1,1,4}{
\draw[white,double=black,very thick,-] (\x,-2) -- (\x,2);
}
\draw[white,double=black,very thick,-] (-3,0) -- (-3,2);
\node[anchor=south] at (-3,2.1) {$z_i^0$};
\draw[decorate sep={1mm}{5mm},fill] (-6.5,0) -- (-4.5,0);
\draw[decorate sep={1mm}{5mm},fill] (1.5,0) -- (3.5,0);
\draw[-] (-8,2) -- (5,2);
\draw[-] (-8,-2) -- (5,-2);
\end{tikzpicture}
\end{document}