diff -r 54b226f7dea3 -r 06f06de6f133 text/a_inf_blob.tex --- a/text/a_inf_blob.tex Sun May 30 00:21:05 2010 -0700 +++ b/text/a_inf_blob.tex Sun May 30 08:49:27 2010 -0700 @@ -22,7 +22,7 @@ \subsection{A product formula} \begin{thm} \label{product_thm} -Given a topological $n$-category $C$ and a $n-k$-manifold $F$, recall from Example \ref{ex:blob-complexes-of-balls} that there is an $A_\infty$ $k$-category $C^{\times F}$ defined by +Given a topological $n$-category $C$ and a $n{-}k$-manifold $F$, recall from Example \ref{ex:blob-complexes-of-balls} that there is an $A_\infty$ $k$-category $C^{\times F}$ defined by \begin{equation*} C^{\times F}(B) = \cB_*(B \times F, C). \end{equation*} @@ -32,9 +32,30 @@ \end{align*} \end{thm} -\begin{question} -Is it possible to compute the blob homology of a non-trivial bundle in terms of the blob homology of its fiber? -\end{question} +\nn{To do: remark on the case of a nontrivial fiber bundle. +I can think of two approaches. +In the first (slick but maybe a little too tautological), we generalize the +notion of an $n$-category to an $n$-category {\it over a space $B$}. +(Should be able to find precedent for this in a paper of PT. +This idea came up in a conversation with him, so maybe should site him.) +In this generalization, we replace the categories of balls with the categories +of balls equipped with maps to $B$. +A fiber bundle $F\to E\to B$ gives an example of such an $n$-category: +assign to $p:D\to B$ the blob complex $\bc_*(p^*(E))$. +We can do the colimit thing over $B$ with coefficients in a n-cat-over-B. +The proof below works essentially unchanged in this case to show that the colimit is the blob complex of the total space $E$. +} + +\nn{The second approach: Choose a decomposition $B = \cup X_i$ +such that the restriction of $E$ to $X_i$ is a product $F\times X_i$. +Choose the product structure as well. +To each codim-1 face $D_i\cap D_j$ we have a bimodule ($S^0$-module). +And more generally to each codim-$j$ face we have an $S^{j-1}$-module. +Decorate the decomposition with these modules and do the colimit. +} + +\nn{There is a version of this last construction for arbitrary maps $E \to B$ +(not necessarily a fibration).} \begin{proof}[Proof of Theorem \ref{product_thm}]