That's essentially wanted.
If you add \showoutput
, you will find, before the first display
...\penalty 10000
...\glue(\abovedisplayskip) 4.89998 plus 4.89998
...\glue(\baselineskip) 2.66669
and after it
...\glue(\belowdisplayskip) 4.89998 plus 4.89998
...\glue -4.89998 plus -4.89998
...\glue 4.89998 plus 4.89998
...\glue -7.89998 plus -4.89998
...\penalty -51
...\glue 3.0
...\glue 4.89998 plus 4.89998
...\glue -4.89998 plus -4.89998
...\glue 7.0 plus 2.79996 minus 2.79996
...\glue(\parskip) 0.0
...\glue(\baselineskip) 2.66669
Before the second display you have
...\penalty 10000
...\glue(\abovedisplayskip) 4.89998 plus 4.89998
...\glue(\lineskip) 1.0
Here \lineskip
is used because the line with the fractions is too high. After the display
...\glue(\belowdisplayskip) 4.89998 plus 4.89998
...\glue -4.89998 plus -4.89998
...\glue 4.89998 plus 4.89998
...\glue -8.89998 plus -4.89998
...\penalty -51
...\glue 4.0
...\glue 4.89998 plus 4.89998
...\glue -4.89998 plus -4.89998
...\glue 7.0 plus 2.79996 minus 2.79996
...\glue(\parskip) 0.0
...\glue(\lineskip) 1.0
and, again, the interline space is \lineskip
.
This would be less noticeable in article
, because amsart
sets \abovedisplayskip
and \belowdisplayskip
to 5pt plus 5pt
instead of 10pt plus 2pt minus 5pt
.
Theorems are not involved in the problem. You get essentially the same with
The following equation holds:
\begin{equation}
\partial_{t} X \wedge \partial_{t} Y_{1} \wedge \dots \wedge
\partial_{t} Y_{n} \wedge Z_{1} \wedge \dotsb \wedge Z_{n} =0 \,.
\end{equation}
The proof of the theorem above is straightforward.
\begin{equation}
\frac{\partial X}{\partial t} \wedge \frac{\partial Y_{1}}{\partial t}
\wedge \dots \wedge \frac{\partial Y_{n}}{\partial t} \wedge Z_{1}
\wedge \dots \wedge Z_{n} =0 \,.
\end{equation}
The proof of the theorem above is straightforward.
The only difference is the management of space after the theorem.
You can “fix” by adding \vspace{1.66667pt}
(or any other value you deem sensible) in the equation with fractions.
\documentclass[a4paper,12pt,oneside,reqno]{amsart}
\usepackage{amssymb}
\theoremstyle{plain}
\newtheorem{theorem}{Theorem}[section]
\newcommand{\fixspace}[1]{%
\setlength{\lineskip}{#1}%
\vspace{#1}%
}
\begin{document}
\begin{theorem}
The following equation holds:
\begin{equation}
\partial_{t} X \wedge \partial_{t} Y_{1} \wedge \dotsb \wedge \partial_{t} Y_{n} \wedge Z_{1} \wedge \dotsb \wedge Z_{n} =0 \,.
\end{equation}
\end{theorem}
The proof of the theorem above is straightforward.
\begin{theorem}
The following equation holds:
\begin{equation}
\frac{\partial X}{\partial t} \wedge \frac{\partial Y_{1}}{\partial t} \wedge \dotsb \wedge \frac{\partial Y_{n}}{\partial t} \wedge Z_{1} \wedge \dotsb \wedge Z_{n} =0 \,.
\fixspace{1.66667pt}
\end{equation}
\end{theorem}
The proof of the theorem above is straightforward.
\end{document}
\medskip
right after\end{theorem}
.