I often want to list a number of short equations (like the non-zero components of a tensor) under a single equation number. To do this I use combinations of the amsmath
environments equation
, gathered
and aligned
. However, for some reason, the different parts of the gathered
environment are not all centered. Consider the example
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{gathered}
\begin{aligned}
q &= r \,, &
x &= y \,, &
z &= w \,,
\end{aligned} \\
\begin{aligned}
A a &= B b \,, &
C c &= D d \,, \\
a &= b \,, &
c &= d \,.
\end{aligned}
\end{gathered}
\end{equation}
\end{document}
I would expect the first two lines both to be centered, but instead they come out more or less aligned at the right hand side. For a real world example consider
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{gathered}
\begin{aligned}
\omega_t{}^{01} = -\omega_t{}^{10} &= \sinh\rho \,, &
\omega_\phi{}^{12} = -\omega_\phi{}^{21} &= -\cosh \rho \,, &
\omega_\rho{}^{AB} &= 0 \,,
\end{aligned} \\
\begin{aligned}
\omega_{\varphi_+}{}^{35} = -\omega_{\varphi_+}{}^{53} &= 2\sin\beta_+ \cos\gamma_+ \,, &
\omega_{\varphi_+}{}^{45} = -\omega_{\varphi_+}{}^{43} &= 2\sin\gamma_+ \,, \\
\omega_{\varphi_-}{}^{68} = -\omega_{\varphi_-}{}^{86} &= 2\sin\beta_- \cos\gamma_- \,, &
\omega_{\varphi_-}{}^{78} = -\omega_{\varphi_-}{}^{87} &= 2\sin\gamma_- \,.
\end{aligned}
\end{gathered}
\end{equation}
\end{document}
Here the first line is pushed even more to the left. It seems like there is some extra space introduced at the end of the first line, but where does this space come from?