# Reduce the gap between \begin{theorem} and [name]

How can we reduce the gap between the number of a theorem and the name of it, for example if we use

\begin{theorem}[Zorn's Lemma]


we have Theorem 0.1 (Zorn's Lemma).

But my goal is to reduce the distance between 0.1 and (Zorn's Lemma).

Theorem 0.1(Zorn's Lemma).

\documentclass[12pt, reqno]{amsart}
\usepackage{amsmath, amsthm, amscd, amsfonts, amssymb, graphicx, color}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\newtheorem{theorem}{Theorem}[section]

\begin{document}

\begin{theorem}[Zorn's Lemma]
If $X$ is a partially ordered set and every linearly ordered subset of $X$ has an upper bound, then $X$ has a maximal element.
\end{theorem}

\vspace{20}
\begin{center}
\textbf{Theorem 0.1}(Zorn's Lemma).
\end{center}

\end{document}

• Why? This doesn't look good. – Alex Sep 22 '13 at 9:22
• Please provide a minimal working example that demonstrate your default behaviour. So we are able to see which package influences the style. – Marco Daniel Sep 22 '13 at 9:24
• Also, specify which theorem environment you are using. The built-in one, package theorem, some AMS package, or something else? – nickie Sep 22 '13 at 9:27
• @Alex: My supervisor emphasizes that this gap should not exist and asked me to remove it in my dissertation, to allow me to graduation. – Empty.Subset Sep 22 '13 at 11:15
• @Empty.Subset: It's always the best to include code inside your question instead of linking any other site. – Marco Daniel Sep 22 '13 at 11:59

As far as your work with the documentclass amsart you don't need to load the packages amsmath or amsthm. The documentation provided the following information at page 2:

Packages. The AMS document classes incorporate the code for the AMS theorem (amsthm) package and automatically load the amsmath package. It is not necessary to request either one explicitly. The user guides for these packages [ATP, AMP] contain the details, which will not be repeated here. The amsfonts package is loaded as well, unless the [noamsfonts] option is specified; see the AMSFonts User’s Guide [AFG] for the features provided.

You request can be solved by redefining the command \thmhead where the space is hard coded.

\makeatletter
\thmname{#1}\thmnumber{\@ifnotempty{#1}{ }\@upn{#2}}%
%  \thmnote{ {\the\thm@notefont(#3)}}}%original
\thmnote{{\the\thm@notefont(#3)}}}%new
\makeatother


Here the complete MWE:

\documentclass[12pt, reqno]{amsart}
\makeatletter
\thmname{#1}\thmnumber{\@ifnotempty{#1}{ }\@upn{#2}}%
\thmnote{{\the\thm@notefont(#3)}}}
\makeatother
\newtheorem{theorem}{Theorem}[section]
\begin{document}

\begin{theorem}[Zorn's Lemma]
If $X$ is a partially ordered set and every linearly ordered subset of $X$ has an upper bound, then $X$ has a maximal element.
\end{theorem}

\vspace{20pt}

\begin{center}
\textbf{Theorem 0.1}(Zorn's Lemma).
\end{center}

\end{document}


However without the space it looks weird.