\normalsize inside \author in class amsart

Question

When I try to compile this MWE in Overleaf (although I should rather say "minimal non-working example"):

\documentclass[12pt,reqno]{amsart}

\title{Title}
\author{\normalsize John Doe}

\begin{document}

\maketitle

\end{document}

I get the following errors:

However, the code compiles correctly as expected if instead we substitute \normalsize by \tiny, \scriptsize, \footnotesize, \small, \large, \LARGE, \huge or \HUGE. So what is happening?

Answer 1

It's clearly bad style to put any formatting in \author as the whole point is to have the author name as text with the style specfied elsewhere in the \maketitle setup, so while probably the macros could be made to avoid this error, removing \normalsize is the correct fix.

That said, you can use \protect to avoid the error.

You get a slightly different error in the current release:

! TeX capacity exceeded, sorry [input stack size=10000].
\__bool_quark_recursion_tail:w ...n_tail #2?#3?!->
                                                  #1#2
l.8 \maketitle
              
!  ==> Fatal error occurred, no output PDF file produced!

but with \protect you get no error:

\documentclass[12pt,reqno]{amsart}

\title{Title}
\author{\protect\normalsize John Doe}

\begin{document}

\maketitle

\end{document}

Answer 2

You don't want \normalsize inside \author, because this would affect also the headers in the even numbered pages.

Better to patch \@setauthors which is responsible for typesetting the authors' names.

\documentclass[12pt,reqno]{amsart}
\usepackage{etoolbox}

\makeatletter
\patchcmd{\@setauthors}{\footnotesize}{\normalsize}{}{}
\makeatother

\title{Title}
\author{John Doe}

\begin{document}

\maketitle

\end{document}