# Drawing arcs under letters

I have been trying to draw something like

Can anyone help me with the code? I have no idea how to do this. Your help would be appreciated.

Edit: Based on comments, I got the code

\documentclass{article}
\usepackage[usenames,dvipsnames]{pstricks}
\usepackage{epsfig}
\usepackage{pst-plot} % For axes
\usepackage[space]{grffile} % For spaces in paths
\usepackage{etoolbox} % For spaces in paths
\makeatletter % For spaces in paths
\makeatother
\documentclass{article}
\usepackage{tikz-cd}
\usepackage{amsmath}
\usetikzlibrary{arrows}

\def\ac{\rotatebox[origin=c]{90}{$\dashv$}} %rotate dash anti-cw
\def\cw{\rotatebox[origin=c]{-90}{$\dashv$}} %rotate dash cw

\begin{document}
\begin{tikzcd}[column sep=small]
q
& &
\arrow[bend left,above]{ll}{a} -q
%\arrow[bend left,above, adj]{ll}{U_G} Cat \arrow[bend left,below]{rr}{F_P}
& &
q
& &
q^2
& &
-q^2\arrow[bend left,above]{ll}{b}
& &
q^2
& &
-q^2\arrow[bend left,above]{ll}{b}
& &
-q
\end{tikzcd}
\end{document}


which gives

But I am not able to draw the big underline.

• Welcome to TeX.SX! Questions about how to draw specific graphics that just post an image of the desired result are really not reasonable questions to ask on the site. Please post a minimal compilable document showing that you've tried to produce the image and then people will be happy to help you with any specific problems you may have. See minimal working example (MWE) for what needs to go into such a document. Dec 14, 2021 at 13:25
• Dec 14, 2021 at 13:30
• Dec 14, 2021 at 13:32

Just add another arrow in a similar fashion you have added the ones.

\documentclass{article}
\usepackage{tikz-cd}
\usepackage{amsmath}
\usetikzlibrary{arrows}

\def\ac{\rotatebox[origin=c]{90}{$\dashv$}} %rotate dash anti-cw
\def\cw{\rotatebox[origin=c]{-90}{$\dashv$}} %rotate dash cw

\begin{document}
\begin{tikzcd}[column sep=small]
q
& &
\arrow[bend left,above]{ll}{a} -q
%\arrow[bend left,above, adj]{ll}{U_G} Cat \arrow[bend left,below]{rr}{F_P}
& &
q
& &
q^2
& &
-q^2\arrow[bend left,above]{ll}{b}
& &
q^2
& &
-q^2\arrow[bend left,above]{ll}{b}
& &
-q\\
&&  &&&&&\\
\end{tikzcd}
\end{document}


• If you don't want an arrowhead, use the option dash in the arrow command like this \arrow[dash, bend left].... Dec 14, 2021 at 14:39