How to put some special diagram in the subscript of a letter?

Question

I'm a newer by using Latex. I don't know how to code the following equation. Can you give me some helpful suggestions?

  _____              ______   
 |                  |
 |___               |____                
 |    _______   .   |      ______    =0
 |    |__|__|       |     |__|___|       
      |__|__|

Answer 1

The usual syntax of using an underscore is not limited to just text, but can be used for graphics as well. Below I have defined \BlockA and \BlockB which produce the two boxes:

If you don't provide any draw options to you get the basic:

Code:

\documentclass{article}  
\usepackage{tikz} 

\begin{document}

\newcommand*{\BlockA}[1][]{%
    % #1 = tikz options
    \begin{tikzpicture}[scale=0.5]
        \draw [#1] (0,0) rectangle (1,1);
        \draw [#1] (0.5,0) -- (0.5,1.0);
        \draw [#1] (0,0.5) -- (1.0,0.5);
    \end{tikzpicture}
}%

\newcommand*{\BlockB}[1][]{%
    % #1 = tikz options
    \begin{tikzpicture}[scale=0.5]
        \draw [#1] (0,0) rectangle (1.0,0.5);
        \draw [#1] (0.5,0) -- (0.5,0.5);
    \end{tikzpicture}
}%

\[
    F_{\BlockA[fill=yellow]} \cdot F_{\BlockB[fill=cyan,draw=red]} = 0
\]
\end{document}