Braid-modular-group-cover.svg


Summary

Description
English: Commutative diagram showing the braid group B 3 as the universal central extension of the modular group , sitting as lattices inside SL 2 ( R ) and its universal cover.
Date
Source Own work, created as per: en:meta:Help:Displaying a formula#Commutative diagrams ; source code below.
Author Nils R. Barth
Permission
( Reusing this file )
Nils R. Barth , the copyright holder of this work, hereby publishes it under the following license:
Public domain I, the copyright holder of this work, release this work into the public domain . This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose , without any conditions, unless such conditions are required by law.

LaTeX source

\documentclass{amsart}
\usepackage[all, ps, dvips]{xy} % Loading the XY-Pic package
                                % Using postscript driver for smoother
                                % curves
\usepackage{color}              % For invisible frame
\DeclareMathOperator{\SL}{SL}
\DeclareMathOperator{\PSL}{PSL}
\begin{document}
\thispagestyle{empty} % No page numbers
\SelectTips{eu}{}     % Euler arrowheads (tips)
\setlength{\fboxsep}{0pt} % Frame box margin
{\color{white}\framebox{{\color{black}$$ % Frame for margin

\xymatrix@R=6pt{
  & B_3  \ar@{->>}[r]  \ar@{^(->}[dd]
  & \PSL_2(\mathbf{Z}) \ar@{^(->}[dd]\\
\mathbf{Z} \ar@{_(->}@/^/[ur] \ar@{^(->}@/_/[dr] \\
  & \overline{\SL_2(\mathbf{R})} \ar@{->>}[r]
  & \PSL_2(\mathbf{R})
}

$$}}} % end math, end frame
\end{document}

Licensing

Public domain I, the copyright holder of this work, release this work into the public domain . This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose , without any conditions, unless such conditions are required by law.

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7 May 2009

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