How to stack nearrow and searrow on top of one another?
Use array
. I set the intercolumn space to zero, but surround \nearrow
and \searrow
with empty subformulas, so the “relation space” is used.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
\setlength{\arraycolsep}{0pt}
\begin{array}{rcl}
&& (b_1,b_2, \dots, b_{l + 1}, \dots, b_{\log N}, l + 1) \\
& {}\nearrow{} \\
(b_1,b_2, \dots, b_{l + 1}, \dots, b_{\log N}, l + 1) \\
& {}\searrow{} \\
&&(b_1,b_2, \dots, \overline{b_{l + 1}}, \dots, b_{\log N}, l + 1)
\end{array}
\end{equation*}
\end{document}
borrowing an idea from henri menke, but rearranging the elements:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
(b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1)
\mkern 9mu \genfrac{}{}{0pt}{}{\nearrow}{\searrow}
\begin{aligned}
& \; (b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1)
\\[.75\baselineskip]
& \; (b_1,b_2, \dots \overline{b_{l + 1}}, \dots b_{\log N}, l + 1)
\end{aligned}
\end{equation*}
\end{document}
Use \genfrac
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
&\; (b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1) \\
(b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1)
\; \genfrac{}{}{0pt}{}{\nearrow}{\searrow} & \\
&\; (b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1)
\end{align*}
\end{document}
or use tikz-cd
\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}
& (b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1) \\
(b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1) \ar[ru] \ar[rd] & \\
& (b_1,b_2, \dots b_{l + 1}, \dots b_{\log N}, l + 1) \\
\end{tikzcd}
\end{document}