我正在创建 Beamer 演示文稿，每当我尝试编译时，都会出现“缺少 $ 插入”错误，我不知道为什么。我研究过此问题的可能解决方案，但没有一个对我有用。有问题的部分如下：
\begin{frame}
\frametitle{Examples}
With this very concrete characterization of the isotropy group of an algebraic theory $\mathbb{T}$ at hand, we can now compute the isotropy groups of several algebraic theories $\mathbb{T}$:
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\begin{itemize}
\item If $\mathbb{T}$ has no axioms, then the isotropy group of $\mathbb{T}$ is trivial, i.e. $\forall M \in \mathbb{T}mod$ we have $\mathcal{Z}_{\mathbb{T}}(M) = \{ [x] \} \cong 1$, the trivial group.
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\item If $\mathbb{T}$ is the theory with one binary commutative or associative operation symbol, then the isotropy group of $\mathbb{T}$ is again trivial.
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\item If $\mathbb{T}$ is the theory of groups, then Bergman essentially proved that $\forall G \in Group$ we have $$ \mathcal{Z}_{\mathbb{T}}(G) = \{ [gxg^{-1}] \in G \langle x \rangle \: \mid g \in G \} \cong G. $$
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\item If $\mathbb{T}$ is the theory of monoids, then $\forall M \in Monoid$ we have $$ \mathcal{Z}_{\mathbb{T}}(M) = \{[mxm'] \in M \langle x \rangle \mid \mbox{ m is invertible in M and m' = m^{-1} } \}. $$
\end{itemize}
\end{frame}
我知道问题出在这一部分，因为当我删除这一部分时，文件能够正确编译。如能得到任何帮助我将不胜感激！
答案1
最后一项有误。正确的是：
\item If $\mathbb{T}$ is the theory of monoids, then $\forall M \in Monoid$ we have
\[
\mathcal{Z}_{\mathbb{T}}(M)
= \{[mxm'] \in M \langle x \rangle \mid \mbox{$m$ is invertible in $M$ and $m' = m^{-1}$} \}.
\]
查看内容的变化mbox（在文本模式下更改）