diff -r 1eab7b40e897 -r a2ff2d278b97 text/ncat.tex --- a/text/ncat.tex Sun Jan 10 20:48:09 2010 +0000 +++ b/text/ncat.tex Wed Jan 27 18:33:59 2010 +0000 @@ -1,6 +1,7 @@ %!TEX root = ../blob1.tex \def\xxpar#1#2{\smallskip\noindent{\bf #1} {\it #2} \smallskip} +\def\mmpar#1#2#3{\smallskip\noindent{\bf #1} (#2). {\it #3} \smallskip} \section{$n$-categories} \label{sec:ncats} @@ -722,12 +723,11 @@ Next we define [$A_\infty$] $n$-category modules (a.k.a.\ representations, a.k.a.\ actions). -The definition will be very similar to that of $n$-categories. +The definition will be very similar to that of $n$-categories, +but with $k$-balls replaced by {\it marked $k$-balls,} defined below. \nn{** need to make sure all revisions of $n$-cat def are also made to module def.} %\nn{should they be called $n$-modules instead of just modules? probably not, but worth considering.} -\nn{** resume revising here} - Our motivating example comes from an $(m{-}n{+}1)$-dimensional manifold $W$ with boundary in the context of an $m{+}1$-dimensional TQFT. Such a $W$ gives rise to a module for the $n$-category associated to $\bd W$. @@ -741,7 +741,7 @@ A homeomorphism between marked $k$-balls is a homeomorphism of balls which restricts to a homeomorphism of markings. -\xxpar{Module morphisms} +\mmpar{Module axiom 1}{Module morphisms} {For each $0 \le k \le n$, we have a functor $\cM_k$ from the category of marked $k$-balls and homeomorphisms to the category of sets and bijections.} @@ -764,14 +764,14 @@ Define the boundary of a marked $k$-ball $(B, N)$ to be the pair $(\bd B \setmin N, \bd N)$. Call such a thing a {marked $k{-}1$-hemisphere}. -\xxpar{Module boundaries, part 1:} +\mmpar{Module axiom 2}{Module boundaries (hemispheres)} {For each $0 \le k \le n-1$, we have a functor $\cM_k$ from the category of marked $k$-hemispheres and homeomorphisms to the category of sets and bijections.} In our example, let $\cM(H) \deq \cD(H\times\bd W \cup \bd H\times W)$. -\xxpar{Module boundaries, part 2:} +\mmpar{Module axiom 3}{Module boundaries (maps)} {For each marked $k$-ball $M$ we have a map of sets $\bd: \cM(M)\to \cM(\bd M)$. These maps, for various $M$, comprise a natural transformation of functors.} @@ -781,14 +781,14 @@ then $\cM(M; c)$ should be an object in that category for each marked $n$-ball $M$ and $c\in \cC(\bd M)$. -\xxpar{Module domain $+$ range $\to$ boundary:} +\mmpar{Module axiom 4}{Boundary from domain and range} {Let $H = M_1 \cup_E M_2$, where $H$ is a marked $k$-hemisphere ($0\le k\le n-1$), $M_i$ is a marked $k$-ball, and $E = M_1\cap M_2$ is a marked $k{-}1$-hemisphere. Let $\cM(M_1) \times_{\cM(E)} \cM(M_2)$ denote the fibered product of the two maps $\bd: \cM(M_i)\to \cM(E)$. Then (axiom) we have an injective map \[ - \gl_E : \cM(M_1) \times_{\cM(E)} \cM(M_2) \to \cM(H) + \gl_E : \cM(M_1) \times_{\cM(E)} \cM(M_2) \hookrightarrow \cM(H) \] which is natural with respect to the actions of homeomorphisms.} @@ -796,7 +796,7 @@ We will refer to elements of $\cM(H)_E$ as ``splittable along $E$" or ``transverse to $E$". -\xxpar{Axiom yet to be named:} +\mmpar{Module axiom 5}{Module to category restrictions} {For each marked $k$-hemisphere $H$ there is a restriction map $\cM(H)\to \cC(H)$. ($\cC(H)$ means apply $\cC$ to the underlying $k$-ball of $H$.)