diff -r fe9295fcf31d -r dfefae16073c text/a_inf_blob.tex --- a/text/a_inf_blob.tex Mon Jun 07 06:01:39 2010 +0200 +++ b/text/a_inf_blob.tex Mon Jun 07 13:43:38 2010 +0200 @@ -106,7 +106,7 @@ filtration degree 1 stuff, and so on. More formally, -\begin{lemma} +\begin{lemma} \label{lem:d-a-acyclic} $D(a)$ is acyclic. \end{lemma} @@ -372,9 +372,66 @@ Ricardo Andrade also told us about a similar result. \end{rem} -\nn{proof is again similar to that of Theorem \ref{product_thm}. should probably say that explicitly} +\begin{proof} +The proof is again similar to that of Theorem \ref{product_thm}. + +We begin by constructing chain map $\psi: \cB^\cT(M) \to C_*(\Maps(M\to T))$. + +Recall that the homotopy colimit $\cB^\cT(M)$ is constructed out of a series of +$j$-fold mapping cylinders, $j \ge 0$. +So, as an abelian group (but not as a chain complex), +\[ + \cB^\cT(M) = \bigoplus_{j\ge 0} C^j, +\] +where $C^j$ denotes the new chains introduced by the $j$-fold mapping cylinders. + +Recall that $C^0$ is a direct sum of chain complexes with the summands indexed by +decompositions of $M$ which have their $n{-}1$-skeletons labeled by $n{-}1$-morphisms +of $\cT$. +Since $\cT = \pi^\infty_{\leq n}(T)$, this means that the summands are indexed by pairs +$(K, \vphi)$, where $K$ is a decomposition of $M$ and $\vphi$ is a continuous +maps from the $n{-}1$-skeleton of $K$ to $T$. +The summand indexed by $(K, \vphi)$ is +\[ + \bigotimes_b D_*(b, \vphi), +\] +where $b$ runs through the $n$-cells of $K$ and $D_*(b, \vphi)$ denotes +chains of maps from $b$ to $T$ compatible with $\vphi$. +We can take the product of these chains of maps to get a chains of maps from +all of $M$ to $K$. +This defines $\psi$ on $C^0$. -\begin{proof} +We define $\psi(C^j) = 0$ for $j > 0$. +It is not hard to see that this defines a chain map from +$\cB^\cT(M)$ to $C_*(\Maps(M\to T))$. + +The image of $\psi$ is the subcomplex $G_*\sub C_*(\Maps(M\to T))$ generated by +families of maps whose support is contained in a disjoint union of balls. +It follows from Lemma \ref{extension_lemma_c} +that $C_*(\Maps(M\to T))$ is homotopic to a subcomplex of $G_*$. + +We will define a map $\phi:G_*\to \cB^\cT(M)$ via acyclic models. +Let $a$ be a generator of $G_*$. +Define $D(a)$ to be the subcomplex of $\cB^\cT(M)$ generated by all +pairs $(b, \ol{K})$, where $b$ is a generator appearing in an iterated boundary of $a$ +and $\ol{K}$ is an index of the homotopy colimit $\cB^\cT(M)$. +(See the proof of Theorem \ref{product_thm} for more details.) +The same proof as of Lemma \ref{lem:d-a-acyclic} shows that $D(a)$ is acyclic. +By the usual acyclic models nonsense, there is a (unique up to homotopy) +map $\phi:G_*\to \cB^\cT(M)$ such that $\phi(a)\in D(a)$. +Furthermore, we may choose $\phi$ such that for all $a$ +\[ + \phi(a) = (a, K) + r +\] +where $(a, K) \in C^0$ and $r\in \bigoplus_{j\ge 1} C^j$. + +It is now easy to see that $\psi\circ\phi$ is the identity on the nose. +Another acyclic models argument shows that $\phi\circ\psi$ is homotopic to the identity. +(See the proof of Theorem \ref{product_thm} for more details.) +\end{proof} + +\noop{ +% old proof (just start): We begin by constructing chain map $g: \cB^\cT(M) \to C_*(\Maps(M\to T))$. We then use Lemma \ref{extension_lemma_c} to show that $g$ induces isomorphisms on homology. @@ -407,8 +464,7 @@ $\cB^\cT(M)$ to $C_*(\Maps(M\to T))$. \nn{...} - -\end{proof} +} \nn{maybe should also mention version where we enrich over spaces rather than chain complexes;}