\vdots between two parallel arrows in \xymatrix

I have the following code

\xymatrix{a􏵥􏵍􏵆􏵤􏵂􏵒􏵀􏴿􏴿\rtwocell^f_g{\omit}&b}


and the result is two arrows from a to b, I want to put \vdots between the two arrows, exactly in the middle (to indicate there are many arrows from a to b). Could anyone help with this?

Other methods not using \xymatrix or 􏵥􏵍􏵆􏵤􏵂􏵒􏵀􏴿􏴿\rtwocell producing horizontal parallel arrows with 3 vertical dots between them is also welcome and is fine for me. What I want is roughly as follows (but I want it to be more symmetric):

I have solved your problem using tikz-cd putting \vdots between the two arrows. I have used sometimes xymatrix.

\documentclass{standalone}
\usepackage{tikz-cd}

\begin{document}
\begin{tikzcd}
Y_{n-1} & Y_n \arrow[l, "d_0"', bend right=42] \arrow[r, draw=none, "\raisebox{+1.5ex}{\vdots}" description]\arrow[l, "d_n", bend left=42] \arrow[r, "s_0", bend left=42]
\arrow[r, "s_n"', bend right=42] \arrow[l, draw=none, "\raisebox{+1.5ex}{\vdots}" description] & Y_{n+1}
\end{tikzcd}
\end{document}


A solution using xypic (and the useful \raisebox command sugested by @Sebastiano). Observe that the vertical dots are aligned with arrow labels.

\documentclass{standalone}
\usepackage[all]{xy}
\begin{document}
$\xymatrix@C=1.5cm{ Y_{n-1} & Y_n \ar@{}[r]|-{\raisebox{+1.5ex}{\vdots}}\ar@{}[l]|-{\raisebox{+1.5ex}{\vdots}} \ar@/_2ex/[r]_-{s_n} \ar@/^2ex/[r]^-{s_0} \ar@/_2ex/[l]_-{d_0} \ar@/^2ex/[l]^-{d_n} & Y_{n+1} }$
\end{document}

• Sigur I really thank you with my heart for quoting my name. Obviously your skill is unexceptionable and you deserve to be given +1. – Sebastiano Oct 9 '18 at 20:28