% Simple commutative diagram
% Author: Stefan Kottwitz
% https://www.packtpub.com/hardware-and-creative/latex-cookbook
\documentclass[border = 5pt]{standalone}
%%%<
\usepackage{verbatim}
%%%>
\begin{comment}
:Title: Simple commutative diagram
:Tags: Mathematics,Graphics;TikZ
:Author: Stefan Kottwitz
:Slug: commutative-diagram
In algebra, especially in category theory, we use so called
commutative diagrams. Vertices denote objects such as groups
or modules. Arrows represent morphisms, which are maps between those objects.
The characteristic quality of such diagrams is that they
commute. This means, you get the same result by composition,
not matter which directed way in the diagram you go,
if start point and end point are the same.
Such diagrams are used a lot for visualizing algebraic properties.
Whole proofs are done by chasing through such a diagram.
That's why our example deals with it. It is a diagram visualizing
the first isomorphism theorem in group theory.
We use the TikZ package, because it offers a wealth of arrow heads
and tails, and useful graphic tools for positioning and labeling.
The code is fully explained in the LaTeX Cookbook, Chapter 10,
Advanced Mathematics, Drawing commutative diagrams.
\end{comment}
\usepackage{tikz}
\usetikzlibrary{matrix,arrows.meta}
\usepackage{amsmath}
\DeclareMathOperator{\im}{im}
\begin{document}
\begin{tikzpicture}
\matrix (m)
[
matrix of math nodes,
row sep = 3em,
column sep = 4em
]
{
G & \im \varphi \\
G/\ker \varphi & \\
};
\path
(m-1-1) edge [->>] node [left] {$\pi$} (m-2-1)
(m-1-1.east |- m-1-2)
edge [->] node [above] {$\varphi$} (m-1-2)
(m-2-1.east) edge [{Hooks[right,length=0.8ex]}->,
dashed] node [below] {$\tilde{\varphi}$} (m-1-2);
\end{tikzpicture}
\end{document}