diff -r 38ceade5cc5d -r b51fcceb1d57 text/ncat.tex --- a/text/ncat.tex Mon Jul 20 17:37:50 2009 +0000 +++ b/text/ncat.tex Mon Jul 20 22:50:59 2009 +0000 @@ -143,5 +143,50 @@ If $k < n$ we require that $\gl_Y$ is injective. (For $k=n$, see below.)} +\xxpar{Strict associativity:} +{The composition (gluing) maps above are strictly associative. +It follows that given a decomposition $B = B_1\cup\cdots\cup B_m$ of a $k$-ball +into small $k$-balls, there is a well-defined +map from an appropriate subset of $\cC(B_1)\times\cdots\times\cC(B_m)$ to $\cC(B)$, +and these various $m$-fold composition maps satisfy an +operad-type associativity condition.} + +\nn{above maybe needs some work} + +The next axiom is related to identity morphisms, though that might not be immediately obvious. + +\xxpar{Product (identity) morphisms:} +{Let $X$ be homeomorphic to a $k$-ball and $D$ be homeomorphic to an $m$-ball, with $k+m \le n$. +Then we have a map $\cC(X)\to \cC(X\times D)$, usually denoted $a\mapsto a\times D$ for $a\in \cC(X)$. +If $f:X\to X'$ and $\tilde{f}:X\times D \to X'\times D'$ are maps such that the diagram +\[ \xymatrix{ + X\times D \ar[r]^{\tilde{f}} \ar[d]^{\pi} & X'\times D' \ar[d]^{\pi} \\ + X \ar[r]^{f} & X' +} \] +commutes, then we have $\tilde{f}(a\times D) = f(a)\times D'$.} + +\nn{Need to say something about compatibility with gluing (of both $X$ and $D$) above.} + +All of the axioms listed above hold for both ordinary $n$-categories and $A_\infty$ $n$-categories. +The last axiom (below), concerning actions of +homeomorphisms in the top dimension $n$, distinguishes the two cases. + +We start with the plain $n$-category case. + +\xxpar{Isotopy invariance in dimension $n$ (preliminary version):} +{Let $X$ be homeomorphic to the $n$-ball and $f: X\to X$ be a homeomorphism which restricts +to the identity on $\bd X$ and is isotopic (rel boundary) to the identity. +Then $f(a) = a$ for all $a\in \cC(X)$.} + + + +\medskip + +\hrule + +\medskip + +\nn{to be continued...} +