diff -r 1d76e832d32f -r 45aceaf20a77 text/ncat.tex --- a/text/ncat.tex Fri Jun 04 17:15:53 2010 -0700 +++ b/text/ncat.tex Fri Jun 04 18:26:04 2010 -0700 @@ -292,6 +292,84 @@ The next axiom is related to identity morphisms, though that might not be immediately obvious. +\begin{axiom}[Product (identity) morphisms, preliminary version] +For each $k$-ball $X$ and $m$-ball $D$, with $k+m \le n$, there is a map $\cC(X)\to \cC(X\times D)$, +usually denoted $a\mapsto a\times D$ for $a\in \cC(X)$. +These maps must satisfy the following conditions. +\begin{enumerate} +\item +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 +\[ + \tilde{f}(a\times D) = f(a)\times D' . +\] +\item +Product morphisms are compatible with gluing (composition) in both factors: +\[ + (a'\times D)\bullet(a''\times D) = (a'\bullet a'')\times D +\] +and +\[ + (a\times D')\bullet(a\times D'') = a\times (D'\bullet D'') . +\] +\item +Product morphisms are associative: +\[ + (a\times D)\times D' = a\times (D\times D') . +\] +(Here we are implicitly using functoriality and the obvious homeomorphism +$(X\times D)\times D' \to X\times(D\times D')$.) +\item +Product morphisms are compatible with restriction: +\[ + \res_{X\times E}(a\times D) = a\times E +\] +for $E\sub \bd D$ and $a\in \cC(X)$. +\end{enumerate} +\end{axiom} + +We will need to strengthen the above preliminary version of the axiom to allow +for products which are ``pinched" in various ways along their boundary. +(See Figure xxxx.) +(The need for a strengthened version will become apparent in appendix \ref{sec:comparing-defs}.) +Define a {\it pinched product} to be a map +\[ + \pi: E\to X +\] +such that $E$ is an $m$-ball, $X$ is a $k$-ball ($k