insert zero height newline

Question

I have the following

\documentclass[12pt,a4paper]{article}
\begin{document}
\begin{align}
 a_{m,m} &\overset{(\eqref{eq:masssplitAIndex},\eqref{eq:masssplitLinvIndex})}{=} 1 - a \\
 &\overset{
  \substack{\eqref{eq:masssplitLinvIndex} \\ % too much space here
            \hphantom{\meqref{eq:masssplitAIndex,eq:masssplitLinvIndex}}
            }
          }
  }{=} 1 - a.
 \end{align}

\end{document}

What is the proper solution to stack (with zero skip) a hphantom box above the (0.33) in the figure such that the spacing to the equal sign is correct?)

take a look at the answer here about \overset: Must be equal and other stacked math symbols — barbara beeton, Aug 20 '15 at 17:22

score 2 · Answer 1 · answered Aug 20 '15 at 17:47

The following example uses \stackrel to put the references above the equals sign. The phantom for the second line is set via \ooalign to avoid the explicit measurement of the references of the previous equation.

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{hyperref}
\numberwithin{equation}{section}

\begin{document}
\setcounter{equation}{32}
\begin{gather}
  \label{eq:masssplitLinvIndex}
  \text{mass split L inv index}
\\
  \label{eq:masssplitAtIndex}
  \text{mass split at index}
\end{gather}

\begin{align}
  a_{m,m}
  & \stackrel{(\ref{eq:masssplitAtIndex},\,\ref{eq:masssplitLinvIndex})}{=}
  1
\\
  & \stackrel{%
      \ooalign{%
        \phantom{%
          $\scriptstyle
          (\ref{eq:masssplitAtIndex},\,\ref{eq:masssplitLinvIndex})$%
        }\cr
        \hfil$\scriptstyle(\ref{eq:masssplitLinvIndex})$\hfil
      }%
    }{=}
  1
\end{align}
\end{document}

score 1 · Answer 2 · edited Apr 13 '17 at 12:34

You can use alignat together with a hack for centering a column's contents:

\documentclass{article}
\usepackage{amsmath,amssymb}

\numberwithin{equation}{section}

\makeatletter
\newcommand{\Cen}[2]{%
  \ifmeasuring@
    #2%
  \else
    \makebox[\ifcase\expandafter #1\maxcolumn@widths\fi]{$\displaystyle#2$}%
  \fi
}
\makeatother

\begin{document}

\setcounter{equation}{32}
\begin{gather}
x\label{eq:masssplitAIndex}\\
y\label{eq:masssplitLinvIndex}
\end{gather}

Now the main thing:
\begin{alignat}{2}
 a_{m,m} &\Cen{2}{\overset{(\ref{eq:masssplitAIndex},\ref{eq:masssplitLinvIndex})}{=}{}} && 1 - a \\
 &\Cen{2}{\overset{\eqref{eq:masssplitLinvIndex}}{=}}&& 1 - a.
\end{alignat}

\end{document}

See https://tex.stackexchange.com/a/209732/4427 for \Cen

However, I'd prefer a simpler thing:

\begin{alignat}{2}
a_{m,m} &= 1-a &&\qquad\text{by (\ref{eq:masssplitAIndex}, \ref{eq:masssplitLinvIndex})} \\
        &= 1-a &&\qquad\text{by \eqref{eq:masssplitLinvIndex}}
\end{alignat}

insert zero height newline

2 Answers2