3

I'm trying to define a new operator (like \bigominus -- but it doesn't exist) to create an equation like

enter image description here

But the problem is that I can't shrink the lower indices after vertical aligning everything that follows. The code I have so far is

\mathop{\huge{\boldsymbol{\ominus}}}\limits_{\tiny{ijk}}\normalsize{\raisebox{0.7ex}{\text{x}[\,u\,][\,v\,][\,w\,]}}

If I remove \raisebox{0.7ex}{} it fixes the indices, but then the vertical alignment is gone.

enter image description here

Obviously it's noticeable with respect to the horizontal line of the symbol. Does anyone know how I may fix this? I would like to either move the \ominus symbol down so that the horizontal line is aligned with the cross of the \text{x}, or the \text{x} and everything that follows so that it aligns with the horizontal line of the \otimes.

I've spent a few hours trying to solve this problem but I cannot seem to find the right command in the rather limited available set from WordPress.

1

You can scale a bold \ominus; whether this works in WordPress I don't know, but it would be off-topic, because WordPress uses MathJax that's not TeX.

\documentclass{article}
\usepackage{amsmath,bm,graphicx}

\makeatletter
\newcommand*{\bigominus}{\DOTSB\bigominus@\slimits@}

\newcommand{\bigominus@}{\mathop{\mathpalette\bigominus@@\relax}}

\newcommand{\bigominus@@}[2]{%
  \vcenter{\hbox{%
    \sbox\z@{$\m@th#1\bigoplus$}%
    \resizebox{\wd\z@}{!}{$\m@th#1\bm{\ominus}$}%
  }}%
}
\makeatother

\begin{document}
\[
\bigominus_{ijk}x[u][v][w]
\qquad
\textstyle
\bigominus_{ijk}x[u][v][w]
\qquad
\scriptstyle
\bigominus_{ijk}x[u][v][w]
\qquad
\scriptscriptstyle
\bigominus_{ijk}x[u][v][w]
\]
\[
\bigoplus_{ijk}x[u][v][w]
\qquad
\textstyle
\bigoplus_{ijk}x[u][v][w]
\qquad
\scriptstyle
\bigoplus_{ijk}x[u][v][w]
\qquad
\scriptscriptstyle
\bigoplus_{ijk}x[u][v][w]
\]

\end{document}

enter image description here

1

\bigominus does exist, in the mathx font of the mathabx package. You can easily use it without having to change the default math font:

\documentclass{article}%
\usepackage[utf8]{inputenc}

\DeclareFontFamily{U}{mathx}{\hyphenchar\font45}
\DeclareFontShape{U}{mathx}{m}{n}{
<-6> mathx5 <6-7> mathx6 <7-8> matha7
<8-9> mathx8 <9-10> mathx9
<10-12> mathx10 <12-> mathx12
}{}
\DeclareSymbolFont{mathx}{U}{mathx}{m}{n}
\DeclareMathSymbol{\bigominus}{\mathop}{mathx}{"C1}

\begin{document}

\[ A \bigominus B \]%

\end{document} 

enter image description here

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