diff -r 2a5d54f51808 -r ae5a542c958e text/hochschild.tex --- a/text/hochschild.tex Wed May 05 22:58:45 2010 -0700 +++ b/text/hochschild.tex Fri May 07 11:18:39 2010 -0700 @@ -416,8 +416,7 @@ and the inclusion $G''_* \sub G'_*$ is a homotopy equivalence. For $G'_*$ the proof is the same as in (\ref{bcontract}), except that the splitting $G'_0 \to H_0(G'_*)$ concentrates the point labels at two points to the right and left of $*$. -For $G''_*$ we note that any cycle is supported \nn{need to establish terminology for this; maybe -in ``basic properties" section above} away from $*$. +For $G''_*$ we note that any cycle is supported away from $*$. Thus any cycle lies in the image of the normal blob complex of a disjoint union of two intervals, which is contractible by (\ref{bcontract}) and (\ref{disj-union-contract}). Finally, it is easy to see that the inclusion @@ -448,13 +447,25 @@ This completes the proof that $i: K''_* \to K'_*$ is a homotopy equivalence. \nn{need to say above more clearly and settle on notation/terminology} -Finally, we show that $K''_*$ is contractible. -\nn{need to also show that $H_0$ is the right thing; easy, but I won't do it now} -Let $x$ be a cycle in $K''_*$. +Finally, we show that $K''_*$ is contractible with $H_0\cong C$. +This is similar to the proof of Proposition \ref{bcontract}, but a bit more +complicated since there is no single blob which contains the support of all blob diagrams +in $K''_*$. +Let $x$ be a cycle of degree greater than zero in $K''_*$. The union of the supports of the diagrams in $x$ does not contain $*$, so there exists a ball $B \subset S^1$ containing the union of the supports and not containing $*$. -Adding $B$ as a blob to $x$ gives a contraction. -\nn{need to say something else in degree zero} +Adding $B$ as an outermost blob to each summand of $x$ gives a chain $y$ with $\bd y = x$. +Thus $H_i(K''_*) \cong 0$ for $i> 0$ and $K''_*$ is contractible. + +To see that $H_0(K''_*) \cong C$, consider the map $p: K''_0 \to C$ which sends a 0-blob +diagram to the product of its labeled points. +$p$ is clearly surjective. +It's also easy to see that $p(\bd K''_1) = 0$. +Finally, if $p(y) = 0$ then there exists a blob $B \sub S^1$ which contains +all of the labeled points (other than *) of all of the summands of $y$. +This allows us to construct $x\in K''_1$ such that $\bd x = y$. +(The label of $B$ is the restriction of $y$ to $B$.) +It follows that $H_0(K''_*) \cong C$. \end{proof} \medskip