starred version of \DeclareMathOperator not working

Question

I am using Kile as my LaTeX editor. I have defined a star for DeclareMathOperator but it does show the behavior of \limits, the subscript appears only in the sides rather than below. But using maptop works \item$\mathop{\inf}\limits_x$. The starred version of operator name is also not working as expected. Please tell me if i am missing something.

Here is my code:

\documentclass[a4paper,10pt]{article}
\usepackage[utf8x]{inputenc}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amsopn}
\DeclareMathOperator*{\argmax}{argmax}                                          % argmax
\DeclareMathOperator*{\argmin}{argmin} 


%opening
\title{Convex Optimization - Points to be clarified}
\author{Venkatesh}


\begin{document}

\section*{Convex sets theory}
\begin{enumerate}
  \item what is a positive semi definite matrix and positive semdi definite cone $S_+^n = \{X \in S^n | X \succeq 0 \}$ ?
  \item what is domain \textbf{dom} $f$ ?
  \item$\mathop{\inf}\limits_x$
  \item$\argmax{_c^b} f(b)$
  \item$\operatorname*{rank}_v(x)$
 \end{enumerate}


\end{document}

Limits in inline formulas are set to the side, by default, and for good reasons. What precisely do you want to get? — egreg, Apr 18 '12 at 12:55
@egreg i never knew this. I am trying to get the subscript in the bottom of the argmin rather than in the side. and i am using only inline mode. is that the issue? — vumaasha, Apr 18 '12 at 13:46
I just verified that it works fine if i embed them between \[ \]. — vumaasha, Apr 18 '12 at 13:56

score 7 · Answer 1 · answered Apr 18 '12 at 13:54

Let's look at some modifications to your input:

\documentclass[a4paper,10pt]{article}
\usepackage[utf8x]{inputenc}
\usepackage{amsfonts}
\usepackage{amsmath}
% \usepackage{amsopn} % amsmath loads this automatically
\DeclareMathOperator*{\argmax}{argmax}                                          % argmax
\DeclareMathOperator*{\argmin}{argmin} 
\DeclareMathOperator{\dom}{\mathbf{dom}}

%opening
\title{Convex Optimization - Points to be clarified}
\author{Venkatesh}


\begin{document}

\section*{Convex sets theory}
\begin{enumerate}
  \item what is a positive semidefinite matrix and positive semidefinite cone $S_+^n = \{X \in S^n \mid X \succeq 0 \}$? % \mid, not |;
  \item what is domain $\dom f$?
  \item$\inf\limits_x$
  \item$\argmax_{c^b} f(b)$
  \item$\operatorname*{rank}_v(x)$
 \end{enumerate}

\end{document}

The \inf operator is predefined. If you want to put the limit under it also in inline formula, put \limits just after it. The same would be true for \argmax; but limits in inline formulas are usually set to the side in order not to make very high or deep lines that would destroy the pagination balance. The \operatorname* defined operators behave just the same as those defined with \DeclareMathOperator*.

Remember never to leave a space before punctuation (unless you're writing in French).

starred version of \DeclareMathOperator not working

1 Answers1