答案1
用一个\parbox
:
\documentclass[twocolumn]{article}
\usepackage{amsmath}
\usepackage{lipsum}
\begin{document}
\lipsum*[2]
\begin{equation}
\partial_{ab}(i,j)=
\begin{cases}
0, & \parbox[t]{.5\displaywidth}{
\raggedright
if $(j,i,a)$ is immediately followed
by the same job that follows $(j,i,b)$}
\\
1, & \text{otherwise}
\end{cases}
\end{equation}
\lipsum
\end{document}