diff -r fdb012a1c8fe -r cc44e5ed2db1 text/comm_alg.tex --- a/text/comm_alg.tex Thu Jul 29 22:44:21 2010 -0400 +++ b/text/comm_alg.tex Fri Jul 30 08:36:25 2010 -0400 @@ -52,11 +52,25 @@ Thus we have defined (up to homotopy) a map from $\bc_*(M, k[t])$ to $C_*(\Sigma^\infty(M))$. -Next we define, for each simplex $c$ of $C_*(\Sigma^\infty(M))$, a contractible subspace +Next we define a map going the other direction. +First we replace $C_*(\Sigma^\infty(M))$ with a homotopy equivalent +subcomplex $S_*$ of small simplices. +Roughly, we define $c\in C_*(\Sigma^\infty(M))$ to be small if the +corresponding track of points in $M$ +is contained in a disjoint union of balls. +Because there could be different, inequivalent choices of such balls, we must a bit more careful. +\nn{this runs into the same issues as in defining evmap. +either refer there for details, or use the simp-space-ish version of the blob complex, +which makes things easier here.} + +\nn{...} + + +We will define, for each simplex $c$ of $S_*$, a contractible subspace $R(c)_* \sub \bc_*(M, k[t])$. If $c$ is a 0-simplex we use the identification of the fields $\cC(M)$ and $\Sigma^\infty(M)$ described above. -Now let $c$ be an $i$-simplex of $\Sigma^j(M)$. +Now let $c$ be an $i$-simplex of $S_*$. Choose a metric on $M$, which induces a metric on $\Sigma^j(M)$. We may assume that the diameter of $c$ is small --- that is, $C_*(\Sigma^j(M))$ is homotopy equivalent to the subcomplex of small simplices. @@ -77,12 +91,13 @@ \begin{prop} \label{ktchprop} -The above maps are compatible with the evaluation map actions of $C_*(\Diff(M))$. +The above maps are compatible with the evaluation map actions of $C_*(\Homeo(M))$. \end{prop} \begin{proof} The actions agree in degree 0, and both are compatible with gluing. (cf. uniqueness statement in Theorem \ref{thm:CH}.) +\nn{if Theorem \ref{thm:CH} is rewritten/rearranged, make sure uniqueness discussion is properly referenced from here} \end{proof} \medskip @@ -93,16 +108,16 @@ \nn{probably should put a more precise statement about cyclic homology and $S^1$ actions in the Hochschild section} Let us check this directly. -The algebra $k[t]$ has Koszul resolution +The algebra $k[t]$ has a resolution $k[t] \tensor k[t] \xrightarrow{t\tensor 1 - 1 \tensor t} k[t] \tensor k[t]$, which has coinvariants $k[t] \xrightarrow{0} k[t]$. -This is equal to its homology, so we have $HH_i(k[t]) \cong k[t]$ for $i=0,1$ and zero for $i\ge 2$. +So we have $HH_i(k[t]) \cong k[t]$ for $i=0,1$ and zero for $i\ge 2$. (See also \cite[3.2.2]{MR1600246}.) This computation also tells us the $t$-gradings: $HH_0(k[t]) \iso k[t]$ is in the usual grading, and $HH_1(k[t]) \iso k[t]$ is shifted up by one. We can define a flow on $\Sigma^j(S^1)$ by having the points repel each other. The fixed points of this flow are the equally spaced configurations. -This defines a map from $\Sigma^j(S^1)$ to $S^1/j$ ($S^1$ modulo a $2\pi/j$ rotation). +This defines a deformation retraction from $\Sigma^j(S^1)$ to $S^1/j$ ($S^1$ modulo a $2\pi/j$ rotation). The fiber of this map is $\Delta^{j-1}$, the $(j-1)$-simplex, and the holonomy of the $\Delta^{j-1}$ bundle over $S^1/j$ is induced by the cyclic permutation of its $j$ vertices. @@ -113,7 +128,7 @@ and is zero for $i\ge 2$. Note that the $j$-grading here matches with the $t$-grading on the algebraic side. -By xxxx and Proposition \ref{ktchprop}, +By Proposition \ref{ktchprop}, the cyclic homology of $k[t]$ is the $S^1$-equivariant homology of $\Sigma^\infty(S^1)$. Up to homotopy, $S^1$ acts by $j$-fold rotation on $\Sigma^j(S^1) \simeq S^1/j$. If $k = \z$, $\Sigma^j(S^1)$ contributes the homology of an infinite lens space: $\z$ in degree @@ -148,7 +163,7 @@ corresponding to $X$. The homology calculation we desire follows easily from this. -\nn{say something about cyclic homology in this case? probably not necessary.} +%\nn{say something about cyclic homology in this case? probably not necessary.} \medskip