diff -r aa7c033bacfa -r d5cbbc87c340 text/ncat.tex --- a/text/ncat.tex Sun Feb 21 03:07:56 2010 +0000 +++ b/text/ncat.tex Sun Feb 21 06:40:00 2010 +0000 @@ -1172,8 +1172,52 @@ Equivalently, we can define 1-sphere modules in terms of 1-marked $k$-balls, $2\le k\le n$. Fix a marked (and labeled) circle $S$. Let $C(S)$ denote the cone of $S$, a marked 2-ball (Figure xxxx). -\nn{I need to make up my mind whether marked things are always labeled too.} -A 1-marked $k$-ball is anything homeomorphic to $B^j \times C(S)$, $0\le j\le n-2$. +\nn{I need to make up my mind whether marked things are always labeled too. +For the time being, let's say they are.} +A 1-marked $k$-ball is anything homeomorphic to $B^j \times C(S)$, $0\le j\le n-2$, +where $B^j$ is the standard $j$-ball. +1-marked $k$-balls can be decomposed in various ways into smaller balls, which are either +smaller 1-marked $k$-balls or the product of an unmarked ball with a marked interval. +We now proceed as in the above module definitions. + +A $n$-category 1-sphere module is, among other things, an $n{-}2$-category $\cD$ with +\[ + \cD(X) \deq \cM(X\times C(S)) . +\] +The product is pinched over the boundary of $C(S)$. +$\cD$ breaks into ``blocks" according to the restriction to the +image of $\bd C(S) = S$ in $X\times C(S)$. + +More generally, consider a 2-manifold $Y$ +(e.g.\ 2-ball or 2-sphere) marked by an embedded 1-complex $K$. +The components of $Y\setminus K$ are labeled by $n$-categories, +the edges of $K$ are labeled by 0-sphere modules, +and the 0-cells of $K$ are labeled by 1-sphere modules. +We can now apply the coend construction and obtain an $n{-}2$-category. +If $Y$ has boundary then this $n{-}2$-category is a module for the $n{-}1$-manifold +associated to the (marked, labeled) boundary of $Y$. +In particular, if $\bd Y$ is a 1-sphere then we get a 1-sphere module as defined above. + +\medskip + +It should now be clear how to define $n$-category $m$-sphere modules for $0\le m \le n-1$. +For example, there is an $n{-}2$-category associated to a marked, labeled 2-sphere, +and an $m$-sphere module is a representation of such an $n{-}2$-category. + +\medskip + +We can now define the $n$- or less dimensional part of our $n{+}1$-category $\cS$. +Choose some collection of $n$-categories, then choose some collections of bimodules for +these $n$-categories, then choose some collection of 1-sphere modules for the various +possible marked 1-spheres labeled by the $n$-categories and bimodules, and so on. +Let $L_i$ denote the collection of $i{-}1$-sphere modules we have chosen. +(For convenience, we declare a $(-1)$-sphere module to be an $n$-category.) +There is a wide range of possibilities. +$L_0$ could contain infinitely many $n$-categories or just one. +For each pair of $n$-categories in $L_0$, $L_1$ could contain no bimodules at all or +it could contain several. + +\nn{...} \medskip \hrule @@ -1187,8 +1231,7 @@ a separate paper): \begin{itemize} \item spell out what difference (if any) Top vs PL vs Smooth makes -\item define $n{+}1$-cat of $n$-cats (a.k.a.\ $n{+}1$-category of generalized bimodules -a.k.a.\ $n{+}1$-category of sphere modules); discuss Morita equivalence +\item discuss Morita equivalence \item morphisms of modules; show that it's adjoint to tensor product (need to define dual module for this) \item functors