diff -r c46b2a01e789 -r 48b246f6a7ad text/ncat.tex --- a/text/ncat.tex Wed Oct 28 17:30:37 2009 +0000 +++ b/text/ncat.tex Wed Oct 28 21:18:55 2009 +0000 @@ -884,47 +884,51 @@ It is not hard to see that the assignment $D \mapsto \cT(W, \cN)(D) \deq \cC(D\times W, \cN)$ has the structure of an $n{-}k$-category. -We will use a simple special case of this construction in the next subsection to define tensor products -of modules. + +\medskip + + +%\subsection{Tensor products} -\subsection{Tensor products} +We will use a simple special case of the above +construction to define tensor products +of modules. +Let $\cM_1$ and $\cM_2$ be modules for an $n$-category $\cC$. +(If $k=1$ and manifolds are oriented, then one should be +a left module and the other a right module.) +Choose a 1-ball $J$, and label the two boundary points of $J$ by $\cM_1$ and $\cM_2$. +Define the tensor product of $\cM_1$ and $\cM_2$ to be the +$n{-}1$-category $\cT(J, \cM_1, \cM_2)$, +\[ + \cM_1\otimes \cM_2 \deq \cT(J, \cM_1, \cM_2) . +\] +This of course depends (functorially) +on the choice of 1-ball $J$. -Next we consider tensor products. +We will define a more general self tensor product (categorified coend) below. + -\nn{what about self tensor products /coends ?} + + +%\nn{what about self tensor products /coends ?} \nn{maybe ``tensor product" is not the best name?} -\nn{start with (less general) tensor products; maybe change this later} - - -Let $\cM$ and $\cM'$ be modules for an $n$-category $\cC$. -(If $k=1$ and manifolds are oriented, then one should be -a left module and the other a right module.) -We will define an $n{-}1$-category $\cM\ot_\cC\cM'$, which depends (functorially) -on a choice of 1-ball (interval) $J$. - -Let $p$ and $p'$ be the boundary points of $J$. -Given a $k$-ball $X$, let $(X\times J, \cM, \cM')$ denote $X\times J$ with -$X\times\{p\}$ labeled by $\cM$ and $X\times\{p'\}$ labeled by $\cM'$, as in Subsection \ref{moddecss}. -Let -\[ - \cT(X) \deq \cC(X\times J, \cM, \cM') , -\] -where the right hand side is the colimit construction defined in Subsection \ref{moddecss}. -It is not hard to see that $\cT$ becomes an $n{-}1$-category. -\nn{maybe follows from stuff (not yet written) in previous subsection?} +%\nn{start with (less general) tensor products; maybe change this later} \subsection{The $n{+}1$-category of sphere modules} + + Outline: \begin{itemize} \item \end{itemize} +\nn{need to assume a little extra structure to define the top ($n+1$) part (?)} \medskip \hrule