[Tex/LaTex] Newlines after section headings in amsart

amsartline-breakingsectioning

This latex code:

\documentclass[9pt]{amsart}

\begin{document}
  \subsubsection*{Animals}
  Rabbit horse monkey cow
\end{document}

Generates something that looks approximately like this:

Animals. Rabbit horse monkey cow.

I'd like to add a newline after the section heading, but if I use \\ with

\subsubsection*{Animals}\

I get:

! LaTeX Error: There's no line here to end.

If I put the \\ inside the brackets, with Animals, then I get a newline but it separates "Animals" from the period:

Animals

. Rabbit horse monkey cow.

How can I put a newline after the section heading without separating it from the period?

EDIT: A good solution is provided below using redefinition of \subsubsection, but a simpler method is to do

\subsubsection*{Animals}\hspace*{\fill} \\
Rabbit horse monkey cow.

Best Answer

You can redefine \subsubsection appropriately; here's the original definition in amsart.cls

\def\subsubsection{\@startsection{subsubsection}{3}%
  \z@{.5\linespacing\@plus.7\linespacing}{-.5em}%
  {\normalfont\itshape}}

and you can redefine it using something like this:

\documentclass[9pt]{amsart}
\usepackage[parfill]{parskip}    

\makeatletter
\def\subsubsection{\@startsection{subsubsection}{3}%
  \z@{.5\linespacing\@plus.7\linespacing}{.1\linespacing}%
  {\normalfont\itshape}}
\makeatother

\begin{document}
\subsubsection*{Animals}
Rabbit horse monkey cow
\end{document}

enter image description here

Another option, not requiring knowing the inner definition of \subsubsection, is to use the titlesec package:

\documentclass[9pt]{amsart}
\usepackage[parfill]{parskip}
\usepackage{titlesec}

\titleformat{\subsubsection}
  {\normalfont\normalsize\itshape}{\thesubsubsection}{1em}{}
\titlespacing*{\subsubsection}{0pt}{3.25ex plus 1ex minus .2ex}{0ex plus .2ex}

\begin{document}
\subsubsection*{Animals}
Rabbit horse monkey cow
\end{document}

However, if you are writing a paper for a submission to an AMS journal, pay attention to the following warning from barbara beeton regarding the use of titlesec with the AMS document classes:

i can't recommend titlesec because it's an option we don't permit when a paper is submitted to an ams journal, so we've never tested it. (for the same reason, i can't "unrecommend" it either. for whatever it's worth, it has never been identified as causing failures with amsart; just "not tested here".)

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