[Tex/LaTex] space in math mode

math-modespacing

I want to obtain the below output from below code:

arg max probability i
i ∈ child(v)

I have the below code:

\documentclass[runningheads,a4paper]{llncs}

\usepackage{amssymb}
\setcounter{tocdepth}{2}
\usepackage{graphicx}
\usepackage[latin1]{inputenc}
\usepackage[english]{babel}
\usepackage{url}

\usepackage{float}
\usepackage{booktabs}
\usepackage{multirow}% http://ctan.org/pkg/multirow
\usepackage{hhline}% http://ctan.org/pkg/hhline

\usepackage{mathtools}

\usepackage{amsmath}
\usepackage[english]{babel}
\usepackage{booktabs,array}



\usepackage{lipsum}
\setcounter{secnumdepth}{5}
\begin{document}


\begin{align*}
         arg \! max \! probability \! i   \\
           i \in \! child(V)
\end{align*}

\end{document}

but the result does not make space in the first line

argmaxprobabilityi
i∈child(V)

How can i fix the missed spaces?

Best Answer

\! creates a small negative space (i.e. moves things closer together). You could use \, for a small space, or just \ (or ~) for a bigger space.

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator\prb{probability}
\DeclareMathOperator\child{child}
\begin{document}
\begin{align*}
         \arg \ \max \ \prb \ i   \\
           i \in \ \child(V)
\end{align*}
\end{document}

enter image description here

Note the use of \DeclareMathOperator from the amsmath package to get the correct spacing and fonts for 'probability' and 'child'. You don't need this for 'arg' or 'max' because those commands are already defined.

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