diff -r b98790f0282e -r 591265710e18 text/appendixes/moam.tex --- a/text/appendixes/moam.tex Wed Jul 28 13:39:52 2010 -0700 +++ b/text/appendixes/moam.tex Thu Jul 29 19:48:59 2010 -0400 @@ -1,4 +1,40 @@ %!TEX root = ../../blob1.tex \section{The method of acyclic models} \label{sec:moam} -\todo{...} \ No newline at end of file + +Let $F_*$ and $G_*$ be chain complexes. +Assume $F_k$ has a basis $\{x_{kj}\}$ +(that is, $F_*$ is free and we have specified a basis). +(In our applications, $\{x_{kj}\}$ will typically be singular $k$-simplices or +$k$-blob diagrams.) +For each basis element $x_{kj}$ assume we have specified a ``target" $D^{kj}_*\sub G_*$. + +We say that a chain map $f:F_*\to G_*$ is {\it compatible} with the above data (basis and targets) +if $f(x_{kj})\in D^{kj}_*$ for all $k$ and $j$. +Let $\Compat(D^\bullet_*)$ denote the subcomplex of maps from $F_*$ to $G_*$ +such that the image of each higher homotopy applied to $x_{kj}$ lies in $D^{kj}_*$. + +\begin{thm}[Acyclic models] +Suppose +\begin{itemize} +\item $D^{k-1,l}_* \sub D^{kj}_*$ whenever $x_{k-1,l}$ occurs in $\bd x_{kj}$ +with non-zero coefficient; +\item $D^{0j}_0$ is non-empty for all $j$; and +\item $D^{kj}_*$ is $(k{-}1)$-acyclic (i.e.\ $H_{k-1}(D^{kj}_*) = 0$) for all $k,j$ . +\end{itemize} +Then $\Compat(D^\bullet_*)$ is non-empty. +If, in addition, +\begin{itemize} +\item $D^{kj}_*$ is $m$-acyclic for $k\le m \le k+i$ and for all $k,j$, +\end{itemize} +then $\Compat(D^\bullet_*)$ is $i$-connected. +\end{thm} + +\begin{proof} +(Sketch) +This is a standard result; see, for example, \nn{need citations}. + +We will build a chain map $f\in \Compat(D^\bullet_*)$ inductively. +Choose $f(x_{0j})\in D^{0j}_0$ for all $j$. +\nn{...} +\end{proof} \ No newline at end of file