diff -r 57bd9fab3827 -r 001fc6183d19 pnas/pnas.tex --- a/pnas/pnas.tex Mon Nov 22 17:55:32 2010 -0700 +++ b/pnas/pnas.tex Mon Nov 22 19:42:06 2010 -0700 @@ -639,21 +639,34 @@ each $B_i$ appears as a connected component of one of the $M_j$. Note that this forces the balls to be pairwise either disjoint or nested. Such a collection of balls cuts $W$ into pieces, the connected components of $W \setminus \bigcup \bdy B_i$. -These pieces need not be manifolds, but they do automatically have permissible decompositions. +These pieces need not be manifolds, +but they can be further subdivided into pieces which are manifolds +and which fit into a permissible decomposition of $W$. The $k$-blob group $\bc_k(W; \cC)$ is generated by the $k$-blob diagrams. A $k$-blob diagram consists of \begin{itemize} -\item a permissible collection of $k$ embedded balls, and -\item for each resulting piece of $W$, a field, + \item a permissible collection of $k$ embedded balls, and + \item a linear combination $s$ of string diagrams on $W$, \end{itemize} -such that for any innermost blob $B$, the field on $B$ goes to zero under the gluing map from $\cC$. -We call such a field a ``null field on $B$". +such that +\begin{itemize} + \item there is a permissible decomposition of $W$, compatible with the $k$ blobs, such that + $s$ is the product of linear combinations of string diagrams $s_i$ on the initial pieces $X_i$ of the decomposition + (for fixed restrictions to the boundaries of the pieces), + \item the $s_i$'s corresponding to innermost blobs evaluate to zero in $\cC$, and + \item the $s_i$'s corresponding to the other pieces are single string diagrams (linear combinations with only one term). +\end{itemize} +%that for any innermost blob $B$, the field on $B$ goes to zero under the gluing map from $\cC$. +\nn{yech} +We call such linear combinations which evaluate to zero on a blob $B$ a ``null field on $B$". The differential acts on a $k$-blob diagram by summing over ways to forget one of the $k$ blobs, with alternating signs. +\nn{KW: I have not finished changng terminology from ``field" to ``string diagram"} + We now spell this out for some small values of $k$. -For $k=0$, the $0$-blob group is simply fields on $W$. +For $k=0$, the $0$-blob group is simply linear combinations of string diagrams on $W$. For $k=1$, a generator consists of a field on $W$ and a ball, such that the restriction of the field to that ball is a null field. The differential simply forgets the ball. Thus we see that $H_0$ of the blob complex is the quotient of fields by fields which are null on some ball.