# [texhax] question

Barbara Beeton bnb at ams.org
Wed Jan 30 18:11:43 CET 2013

hello, antonio,

I have a vexing problem with latex as described in the attending file.
I am not technically competent, but an applied mathematician struggling to
arrive at a decent manuscript. Can you help?

the problem is with the math expression in the
\section text of the file III62.tex.

here is what you have (line breaks added):

\section{The  case of vector processes:
$\underline{X}=S\left[\underline{a}\right] +\underline{B}$}

the section heading is what is called a
"moving argument" -- this data is saved
and inserted (in the book class) into a
running head.  if any command in a moving
argument is "fragile", it will cause a
problem, and not always in an obvious way.
that is what is happening here.

the command \underline is fragile, and the
way to fix it is, whenever it is in a moving
argument, to "protect" it.  this is done by
inserting the command \protect just before
the fragile command:

\section{The  case of vector processes:
$\protect\underline{X}=S\left[\protect\underline{a}\right] +\protect\underline{B}$}

this should solve your problem.

other commands with moving arguments are
any "section" heading (\chapter, \subsection,
...), \caption, and \footnote.

while the recommendation from william adams
won't solve your current problem, it's good
advice, and you should consider adopting it.
also, i think you would benefit from reading
some basic latex documentation.  some good
resources are "the not so short guide" (if
you have a tex live installation, you can
access this by typing
texdoc lshort
at the command line, or you can see it from
ctan -- go to
http://www.ctan.org/search/
and enter  lshort  as the search argument)
and the documentation for amsmath,
texdoc amsldoc
or
ftp://ftp.ams.org/pub/tex/doc/amsmath/amsldoc.pdf

good luck.
-- bb


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