Represent an arc over letters

Question

I want to have a flat arc over some letters. How is it possible?

\documentclass{article}
\usepackage{graphicx,amsmath}
\newcommand\bigfrown[2][\textstyle]{\ensuremath{%
  \array[b]{c}\text{\scalebox{2.4}{$#1\frown$}}\\[-1.3ex]#1#2\endarray}}

\begin{document}

\bigfrown{PQR}    

\end{document}

Answer 1

Instead of scalebox you may use resizebox

\documentclass{article}
\usepackage{graphicx,amsmath}
\newcommand\bigfrown[2][\textstyle]{\ensuremath{%
  \array[b]{c}\text{\resizebox{6ex}{.7ex}{$#1\frown$}}\\[-1.3ex]#1#2\endarray}}

\begin{document}

\bigfrown{PQR}


\end{document}

This is very manual and you have to adjust the parameters of resizebox by yourself.

Edit:

Atleast with this code you don't have to guess the width:

\documentclass{article}
\usepackage{graphicx,amsmath,calc}
\newlength{\mywidth}
\newcommand\bigfrown[2][\textstyle]{\ensuremath{%
  \array[b]{c}\text{\resizebox{\mywidth}{.7ex}{$#1\frown$}}\\[-1.3ex]#1#2\endarray}}

\begin{document}
\settowidth{\mywidth}{PQRSPQ}
\bigfrown{PQRSPQ}

%\setlength{\mywidth}{0pt}
\settowidth{\mywidth}{PQR}
\bigfrown{PQR}


\end{document}