Labels closer to the arrows with xy package

Question

Few hours ago I have added my answer for this question How to make a math diagram on LaTex?

\documentclass[12pt]{standalone}
\usepackage[all,cmtip]{xy}
\usepackage[bb = boondox]{mathalfa}
\begin{document}
\xymatrix@R=.6pc@C=.6pc
   { & \mathbb{F} \ar[dl]_{\scriptscriptstyle\mu} \ar[dr]^{\scriptscriptstyle\nu}  & \\
     \mathbb{P} & & \mathbb{M}
   }
\end{document} 

but the labels are a little too far from the arrows. I have not found in the manual what I am looking for. Is there a way to bring the labels closer to the arrows?

Answer 1

Here is a possible solution. You have to set the values by hand.

The idea is to print the default arrow with no labels and then insert an invisible arrow translated by some amount in parallel, with the label on it.

Observe the \ar[dl] \ar@<3pt>@{}[dl]_{}.

\documentclass[12pt]{standalone}
\usepackage[all,cmtip]{xy}
\usepackage[bb = boondox]{mathalfa}
\begin{document}
$\xymatrix@R=.6pc@C=.6pc{
& \mathbb{F}    \ar[dl] \ar@<3pt>@{}[dl]_{\scriptscriptstyle\mu} 
                \ar[dr] \ar@<-3pt>@{}[dr]^{\scriptscriptstyle\nu}
& \\
\mathbb{P} & & \mathbb{M}
}$
\end{document} 

Answer 2

Use \labelmargin, see 24i on page 40 of the reference manual.

\documentclass[12pt]{standalone}
\usepackage[all,cmtip]{xy}
\usepackage[bb = boondox]{mathalfa}

\begin{document}

\xymatrix@R=.6pc@C=.6pc{
 & \mathbb{F} \ar[dl]_{\scriptscriptstyle\mu}
              \ar[dr]^{\scriptscriptstyle\nu}  & \\
   \mathbb{P} & & \mathbb{M}
}

\labelmargin-{2pt}

\xymatrix@R=.6pc@C=.6pc{
 & \mathbb{F} \ar[dl]_{\scriptscriptstyle\mu}
              \ar[dr]^{\scriptscriptstyle\nu}  & \\
   \mathbb{P} & & \mathbb{M}
}

\end{document}