[Tex/LaTex] Left sided subscript with \mel of physics package

bracketsphysics

I want to tex the following MWE:

\documentclass[
amsmath,
onecolumn,
aps,
prb,
notitlepage,
10pt
]{revtex4-1}

\usepackage{physics}

\newcommand{\mrm}[1]{\mathrm{#1}}
\newcommand{\eps}{\epsilon}

\begin{document}

\begin{align}
\abs{ _u\mel{\nu,\vb*{0}}{\vb*{k}\cdot\vb*{p}}{\nu',\vb*{0}}_u }^2
\end{align}

\end{document}

Output

The problem is in the that the u in front of the matrix element (\mel is from the physics package) is too far away from the left bracket (<). Can I somehow reduce that space?

Best Answer

A solution using mathtools:

\documentclass{revtex4-1}

\usepackage{mathtools}

\DeclarePairedDelimiter\abs{\lvert}{\rvert}
\DeclarePairedDelimiterX\phys[3]{\langle}{\rangle}{#1 \delimsize\vert\mathopen{} #2 \delimsize\vert\mathopen{} #3}
\newcommand*\Vector[1]{\boldsymbol{#1}}

\begin{document}

\begin{equation}
  \abs*{\prescript{}{u}{\phys*{\nu,\Vector{0}}{\Vector{k} \cdot \Vector{p}}{\nu',\Vector{0}}}_{u}}^{2}
\end{equation}

\end{document}

output

For your particular problem, the \prescript macro is the key.

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