# TikZ braids package: inserting identities/space in braid diagrams

I am using the braids package (https://www.ctan.org/pkg/braids) by Andrew Stacey to draw braid diagrams with TikZ. With this package, the braid is specified by a braid word. However, I haven't found a way to add identities to the braid, i.e. to space out different components of the braid word, like e.g. in the middle part of the left diagram (which is from the package documentation):

At the moment I have the diagram on the right, corresponding to the code

\documentclass[a4paper]{scrartcl}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}
\usepackage{braids}

\begin{document}

\begin{tikzpicture}
\braid[number of strands=4] (braid) a_2 a_3 a_3 a_2;
\end{tikzpicture}

\end{document}


Is there a way to add a specified (arbitrary) amount of space between the two a_3? More generally, how can I add arbitrary space (= identity maps) before or after any crossing in a braid diagram?

• Have you read this question and seen if the package described there suites you?. Welcome to TeX.SE! Apr 15, 2017 at 20:38
• @Moriambar Yes, I found this question, but I would like to stick to the braids package if possible. Apr 15, 2017 at 20:52

The version of braids that is available on github introduces the symbol 1 to the braid word, meaning that it is possible to specify a segment with no crossings whatsoever.

Taking Ulrike's example, this could be rewritten as:

\documentclass[a4paper]{scrartcl}

\usepackage{tikz}
\usepackage{braids}

\begin{document}

\begin{tikzpicture}
\braid a_2 a_3 1 1 1 a_3 a_2;
\end{tikzpicture}

\end{document}


Assuming that you don't want to enlarge the height of all groups I think you need a "dummy" strand. Be aware that it changes the bounding box of the graphic, so you need to adapt it.

\documentclass[a4paper]{scrartcl}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}
\usepackage{braids}

\begin{document}

\begin{tikzpicture}
\braid[number of strands=4,
style strands={5,6}{draw=none}] (braid) a_2 a_3 a_5 a_5 a_5 a_3 a_2;
\end{tikzpicture}

\end{document}


• a_{-1} produces the same effect. Apr 15, 2017 at 22:13