[Tex/LaTex] Annoying space before the first item in an enumeration which starts a theorem

listsspacingtheorems

Consider the following example:

\documentclass{article}
\newtheorem{Theorem}{Theorem}
\begin{document}
\begin{Theorem}
On the other hand, this one has only one claim.
\end{Theorem}
\begin{Theorem}
\begin{enumerate}
\item First claim
\item Second claim
\end{enumerate}
\end{Theorem}
\end{document}

Typesetting it results in:

enter image description here

Notice there is extra horizontal space before the first item in the list of the second theorem.

Is there a sensible way to get rid of that?

Ideally, the solution would work with amsthm, thmtools, enumitem.

N.B.: this is related to Is it possible to skip the first line in a theorem environment? but not quite the same.

Best Answer

Two variants of a solution using the enumitem package. In the first case, two enumerate environments were used; the first one uses leftamargin=* to suppress the undesired horizontal space; the second enumerate uses resume to keep the numbering but preserves the standard value for \leftmargin; the vertical spacing between the two environments was also corrected. In the second case, the option leftmargin=* was also used, but this time only one enumerate environment was used so the horizontal space will be removed for all the items.

\documentclass{article}
\usepackage{enumitem}

\newtheorem{Theorem}{Theorem}

\begin{document}

\begin{Theorem}
   On the other hand, this one has only one claim.
\end{Theorem}

\begin{Theorem}
  \begin{enumerate}[leftmargin=*]
    \item First claim
  \end{enumerate}\vspace*{-2\partopsep}
  \begin{enumerate}[resume]
    \item Second claim
  \end{enumerate}
\end{Theorem}

\begin{Theorem}
   On the other hand, this one has only one claim.
\end{Theorem}

\begin{Theorem}
  \begin{enumerate}[leftmargin=*]
    \item First claim
    \item Second claim
  \end{enumerate}
\end{Theorem}

\end{document}

The result:

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