gauge-link-forward.tex

% Copyright © 2017-2018 Martin Ueding <martin-ueding.de>
% Licensed under CC-BY 4.0

\documentclass{scrartcl}

\pagestyle{empty}

\usepackage{tikz}

\usetikzlibrary{arrows.meta}
\usetikzlibrary{calc}
\usetikzlibrary{positioning}
\usetikzlibrary{decorations}
\usetikzlibrary{decorations.markings}

\begin{document}


\tikzset{
    gauge link/.style={
        %thick,
    },
    link arrow/.style={
        decoration={
            markings,
            mark=at position 0.0 with {\arrow{Straight Barb}},
        },
        postaction={decorate},
    },
    link arrow midway/.style={
        decoration={
            markings,
            mark=at position 0.5 with {\arrow{Straight Barb}},
        },
        postaction={decorate},
    },
    gauge link arrow/.style={
        gauge link,
        link arrow midway,
    },
    lattice point/.style={
        draw,
        fill,
        circle,
        minimum size=1.7mm,
        inner sep=0,
    },
}

\begin{tikzpicture}
    \node[lattice point] (n) at (0, 0) {};
    \node[below left=0.5mm of n] {$\vec n$};
    \node[lattice point] (n-mu) at (30mm, 0) {};
    \node[below right=0.5mm of n-mu] {$\vec n + \mu$};

    \draw[gauge link] (n) -- ++(-4mm, 0);
    \draw[gauge link] (n) -- ++(0, 4mm);
    \draw[gauge link] (n) -- ++(0, -4mm);

    \draw[gauge link] (n-mu) -- ++(4mm, 0);
    \draw[gauge link] (n-mu) -- ++(0, 4mm);
    \draw[gauge link] (n-mu) -- ++(0, -4mm);

    \draw[gauge link arrow, thick] (n) -- (n-mu) node[below, midway] {$U_\mu(\vec n)$};
\end{tikzpicture}

\end{document}