\documentclass{amsart}
\newtheorem{proposition}{Proposition}
\begin{document}
\begin{proposition}[Algebraic Structure of $F[x]$]
This is a proposition.
\end{proposition}
\end{document}
但这没用
答案1
\documentclass{amsart}
\newtheorem{proposition}{Proposition}
\begin{document}
\begin{proposition}[Algebraic Structure of $F\lbrack x\rbrack$]
This is a proposition.
\end{proposition}
\end{document}