Question: In the following example instead of `\underbrace`, I want to use something like `\text bar\leftarrow j+1\rightarrow\textbar`. 

`(p_{1},p_{2}\ldots,p_{m-j},\underbrace{m,m,\dots,m}_{j+1})`

Is there any similar command?

Answer: 
You can use `\underset` from [`amsmath`](http://ctan.org/pkg/amsmath):

![enter image description here](https://i.stack.imgur.com/5Kyae.png)

```
\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
$(p_{1},p_{2}\ldots,p_{m-j},\underbrace{m,m,\dots,m}_{j+1})$ \par
$(p_{1},p_{2}\ldots,p_{m-j},\underset{\leftarrow\hfill j+1\hfill\rightarrow}{m,m,\dots,m})$ \par
$(p_{1},p_{2}\ldots,p_{m-j},\underset{\text{\textbar}\leftarrow\hfill j+1\hfill\rightarrow\text{\textbar}}{m,m,\dots,m})$
\end{document}

```
If you want to be able to get a bit fancier, there is *always* the `tikz` way. This `\UnderArrow` macro will auto adjust for the longer texts either above or as part of the text below, and also allows you to apply styling to the lines and arrows:

![enter image description here](https://i.stack.imgur.com/2SPYZ.png)

Code:
-----

```
\documentclass{article}
\usepackage{tikz}

\newcommand*{\UnderArrow}[3][]{%
    \begin{tikzpicture}[baseline, inner sep=0pt]
        \node [anchor=base]  (A) {$#2$};
        \node [below] (B) at (A.south) {$#3$};
        \begin{scope}[overlay]
            \draw [thick, #1, -] ([xshift=-0.07em]A.south east) -- ++ (0,-2.0ex);
            \draw [thick, #1, -] ([xshift=+0.07em]A.south west) -- ++ (0,-2.0ex);
            \draw [-stealth, #1] (B.west) -- ([xshift=+0.07em]B.west -| A.south west);
            \draw [-stealth, #1] (B.east) -- ([xshift=-0.07em]B.east -| A.south east);
        \end{scope}
    \end{tikzpicture}%
}%

\begin{document}
$(p_{1},p_{2}\ldots,p_{m-j},\UnderArrow{m,m,\dots,m}{j+1})$

\medskip
$(p_{1},p_{2}\ldots,p_{m-j},\UnderArrow[blue]{m,m,\dots,m}{j+k+1})$

\medskip
$(p_{1},p_{2}\ldots,p_{m-j},\UnderArrow[red, -latex]{m,n,o,p,\dots,q,r,s}{j+k+1})$
\end{document}

```