Appropriate parenthesizing of theorem title

Question

Is there a way to ensure that we may use \label{key}[Theoremtitle] while avoiding getting "[Theoremtitle]" and instead getting "(Theoremtitle)" - as with [Theoremtitle]\label{key} in the example below.

Using [Name]\label{key} created problems for the line breaking.

\documentclass{article}
\usepackage{amsthm}
\theoremstyle{remark}
\newtheorem{Theorem}[equation]{\em{ T{\footnotesize HEOREM}}}
\begin{document}
\begin{Theorem}\label{key}[Theoremtitle]
2=2
    \end{Theorem}
\begin{Theorem}[Theoremtitle]\label{key}
    2=2
\end{Theorem}
\end{document}

Are you trying to create the look of small-cap letters? If so, please don't use T{\footnotesize HEOREM}; instead, use \textsc{Theorem}. — Mico, Dec 05 '23 at 19:31
Just out of curiosity: What makes you think it's a good idea to write \begin{Theorem}\label{key}[Theoremtitle] instead of \begin{Theorem}[Theoremtitle] \label{key}? Relatedly, in view of the fact that \label{...} doesn't output anything visible, what's the basis for your claim that \begin{Theorem}[Name]\label{key} "create[s] problems for the line breaking"? — Mico, Dec 05 '23 at 19:55

egreg · Accepted Answer · 2023-12-05T21:03:04.033

3

Main problem: \label must go after the entire theorem header specification. There is no sensible way to support the syntax you seem to want that doesn't really make sense. Moreover

\em doesn't take an argument;
you don't want \em anyway, because the theorem style remark already uses \itshape for the header;
you want proper slanted small caps, not the hack with \footnotesize.

\documentclass{article}
\usepackage{lmodern}
\usepackage{amsthm}
\usepackage{fixcmex}% because of lmodern
\theoremstyle{remark}
\newtheorem{Theorem}[equation]{{\normalfont\scshape\slshape Theorem}}
\begin{document}
\begin{Theorem}[Theoremtitle]\label{key}
Something here.
\end{Theorem}
\end{document}

In a better way:

\documentclass{article}
\usepackage{lmodern}
\usepackage{amsthm}
\usepackage{fixcmex}% because of lmodern
% see https://tex.stackexchange.com/a/17555/4427
\newtheoremstyle{scslheader}
  {\topsep}   % ABOVESPACE
  {\topsep}   % BELOWSPACE
  {\normalfont}  % BODYFONT
  {0pt}       % INDENT (empty value is the same as 0pt)
  {\normalfont} % HEADFONT
  {.}         % HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {\thmname{\textsc{\textsl{#1}}}\thmnumber{ #2}\thmnote{ (#3)}} % CUSTOM-HEAD-SPEC
\theoremstyle{scslheader}
\newtheorem{Theorem}[equation]{Theorem}
\begin{document}
\begin{Theorem}[Theoremtitle]\label{key}
Something here.
\end{Theorem}
\end{document}

edited Dec 05 '23 at 21:03

answered Dec 05 '23 at 20:56

egreg

1,121,712

Thanks! I get the error message Package fixcmex Warning: No change in the math extension font, and do not obtain such changes as you. – Frode Alfson Bjørdal Dec 06 '23 at 18:15
@FrodeAlfsonBjørdal You possibly have an outdated LaTeX distribution. – egreg Dec 06 '23 at 18:17
I write with Overleaf – Frode Alfson Bjørdal Dec 06 '23 at 20:01
@FrodeAlfsonBjørdal What version of TeX LIve? Choose 2023. – egreg Dec 06 '23 at 20:29
Now 2023 chosen. This line {\thmname{\textsc{\textsl{#1}}}\thmnumber{ #2}\thmnote{ (#3)}} % CUSTOM-HEAD-SPEC creates problems. Is it an abbreviation for possible choices to be made somewhere? – Frode Alfson Bjørdal Dec 06 '23 at 21:13
@FrodeAlfsonBjørdal It doesn't cause problems to me. – egreg Dec 06 '23 at 21:29
It may be because my environment persistently causes error for \usepackage{fixcmex}% because of lmodern. I now achieved a good resolution with \newtheorem{Theorem}[equation]{{\large \normalfont\rmfamily\scshape Theorem}} under theorem style Remark. :) – Frode Alfson Bjørdal Dec 06 '23 at 21:52

Mico · Answer 2 · 2023-12-05T19:51:32.223

If I understand your code correctly, you're looking to write "Theorem" with an italic/smallcap lettering combination. The basic Computer Modern/Latin Modern font family doesn't provide such a combination. I suggest you employ the newtxtext and newtxmath packages, which provide a Times Roman clone. Or, consider employing the newpxtext and newpxmath packages, which provide a Palatino clone.

\documentclass{article}
\usepackage{amsthm}
\theoremstyle{remark} % use upright lettering, no extra vertical whitespace space
\newtheorem{Theorem}[equation]{\textit{\textsc{Theorem}}}
\usepackage{newtxtext,newtxmath} 
  % Times Roman clone that provides italic-smallcap combination
\begin{document}
\begin{Theorem}[Theoremtitle] \label{thm:112}
\begin{equation} \label{eq:112}
1+1=2
\end{equation}
\end{Theorem}
\noindent
A cross-reference to Theorem \ref{thm:112}, and another one to equation \eqref{eq:112}.
\end{document}

Appropriate parenthesizing of theorem title

2 Answers2