diff -r 1df2e5b38eb2 -r 4f2ea5eabc8f text/hochschild.tex --- a/text/hochschild.tex Sun May 24 20:30:45 2009 +0000 +++ b/text/hochschild.tex Thu Jun 04 19:28:55 2009 +0000 @@ -4,6 +4,10 @@ and find that for $S^1$ the blob complex is homotopy equivalent to the Hochschild complex of the category (algebroid) that we started with. +\nn{need to be consistent about quasi-isomorphic versus homotopy equivalent +in this section. +since the various complexes are free, q.i. implies h.e.} + Let $C$ be a *-1-category. Then specializing the definitions from above to the case $n=1$ we have: \begin{itemize} @@ -53,7 +57,7 @@ \begin{lem} \label{lem:module-blob}% The complex $K_*(C)$ (here $C$ is being thought of as a -$C$-$C$-bimodule, not a category) is quasi-isomorphic to the blob complex +$C$-$C$-bimodule, not a category) is homotopy equivalent to the blob complex $\bc_*(S^1; C)$. (Proof later.) \end{lem} @@ -179,17 +183,28 @@ in $N_\ep$, except perhaps $*$, and $N_\ep$ is either disjoint from or contained in every blob in the diagram. Note that for any chain $x \in \bc_*(S^1)$, $x \in L_*^\ep$ for sufficiently small $\ep$. +\nn{what if * is on boundary of a blob? need preliminary homotopy to prevent this.} We define a degree $1$ chain map $j_\ep: L_*^\ep \to L_*^\ep$ as follows. Let $x \in L_*^\ep$ be a blob diagram. +\nn{maybe add figures illustrating $j_\ep$?} If $*$ is not contained in any twig blob, we define $j_\ep(x)$ by adding $N_\ep$ as a new twig blob, with label $y - s(y)$ where $y$ is the restriction of $x$ to $N_\ep$. If $*$ is contained in a twig blob $B$ with label $u=\sum z_i$, write $y_i$ for the restriction of $z_i$ to $N_\ep$, and let $x_i$ be equal to $x$ on $S^1 \setmin B$, equal to $z_i$ on $B \setmin N_\ep$, and have an additional blob $N_\ep$ with label $y_i - s(y_i)$. Define $j_\ep(x) = \sum x_i$. -\todo{need to check signs coming from blob complex differential} -\todo{finish this} + +It is not hard to show that on $L_*^\ep$ +\[ + \bd j_\ep + j_\ep \bd = \id - i \circ s . +\] +\nn{need to check signs coming from blob complex differential} +Since for $\ep$ small enough $L_*^\ep$ captures all of the +homology of $\bc_*(S^1)$, +it follows that the mapping cone of $i \circ s$ is acyclic and therefore (using the fact that +these complexes are free) $i \circ s$ is homotopic to the identity. \end{proof} + \begin{proof}[Proof of Lemma \ref{lem:hochschild-exact}] We now prove that $K_*$ is an exact functor.