
diff -r 9ace9a326c39 -r a7b53f6a339d text/ncat.tex
--- a/text/ncat.tex	Wed Jun 23 09:41:10 2010 -0700
+++ b/text/ncat.tex	Wed Jun 23 18:37:25 2010 -0700
@@ -1686,9 +1686,12 @@
 but this is much less true for higher dimensional spheres, 
 so we prefer the term ``sphere module" for the general case.
 
+The results of this subsection are not needed for the rest of the paper,
+so we will skimp on details in a couple of places.
+
 For simplicity, we will assume that $n$-categories are enriched over $\c$-vector spaces.
 
-The $0$- through $n$-dimensional parts of $\cC$ are various sorts of modules, and we describe
+The $0$- through $n$-dimensional parts of $\cS$ are various sorts of modules, and we describe
 these first.
 The $n{+}1$-dimensional part of $\cS$ consists of intertwiners
 of (garden-variety) $1$-category modules associated to decorated $n$-balls.
@@ -1987,6 +1990,94 @@
 In other words, the inner product on $Y$ is determined by the inner products on
 $Y_1$, $Y_2$ and $D\times I$.
 
+Now we show how to unambiguously identify $\cS(X; c; E)$ and $\cS(X; c; E')$ for any
+two choices of $E$ and $E'$.
+Consider first the case where $\bd X$ is decomposed as three $n$-balls $A$, $B$ and $C$,
+with $E = \bd(A\cup B)$ and $E' = \bd A$.
+We must provide an isomorphism between $\cS(X; c; E) = \hom(\cS(C), \cS(A\cup B))$
+and $\cS(X; c; E') = \hom(\cS(C\cup \ol{B}), \cS(A))$.
+Let $D = B\cap A$.
+Then as above we can construct a map
+\[
+	\psi: \cS(B)\ot\cS(\ol{B}) \to \cS(D\times I) .
+\]
+Given $f\in \hom(\cS(C), \cS(A\cup B))$ we define $f'\in \hom(\cS(C\cup \ol{B}), \cS(A))$
+to be the composition
+\[
+	\cS(C\cup \ol{B}) \stackrel{f\ot\id}{\longrightarrow}
+		\cS(A\cup B\cup \ol{B})  \stackrel{\id\ot\psi}{\longrightarrow}
+			\cS(A\cup(D\times I)) \stackrel{\cong}{\longrightarrow} \cS(A) .
+\]
+(See Figure xxxx.)
+Let $D' = B\cap C$.
+Using the inner products there is an adjoint map
+\[
+	\psi^\dagger: \cS(D'\times I) \to \cS(\ol{B})\ot\cS(B) .
+\]
+Given $f'\in \hom(\cS(C\cup \ol{B}), \cS(A))$ we define $f\in \hom(\cS(C), \cS(A\cup B))$
+to be the composition
+\[
+	\cS(C) \stackrel{\cong}{\longrightarrow}
+		\cS(C\cup(D'\times I)) \stackrel{\id\ot\psi^\dagger}{\longrightarrow}
+			\cS(C\cup \ol{B}\cup B)   \stackrel{f'\ot\id}{\longrightarrow}
+				\cS(A\cup B) .
+\]
+It is not hard too show that the above two maps are mutually inverse.
+
+\begin{lem}
+Any two choices of $E$ and $E'$ are related by a series of modifications as above.
+\end{lem}
+
+\begin{proof}
+(Sketch)
+$E$ and $E'$ are isotopic, and any isotopy is 
+homotopic to a composition of small isotopies which are either
+(a) supported away from $E$, or (b) modify $E$ in the simple manner described above.
+\end{proof}
+
+It follows from the lemma that we can construct an isomorphism
+between $\cS(X; c; E)$ and $\cS(X; c; E')$ for any pair $E$, $E'$.
+This construction involves on a choice of simple ``moves" (as above) to transform
+$E$ to $E'$.
+We must now show that the isomorphism does not depend on this choice.
+We will show below that it suffice to check two ``movie moves".
+
+The first movie move is to push $E$ across an $n$-ball $B$ as above, then push it back.
+The result is equivalent to doing nothing.
+As we remarked above, the isomorphisms corresponding to these two pushes are mutually
+inverse, so we have invariance under this movie move.
+
+The second movie move replaces to successive pushes in the same direction,
+across $B_1$ and $B_2$, say, with a single push across $B_1\cup B_2$.
+(See Figure xxxx.)
+Invariance under this movie move follows from the compatibility of the inner
+product for $B_1\cup B_2$ with the inner products for $B_1$ and $B_2$.
+
+If $n\ge 2$, these two movie move suffice:
+
+\begin{lem}
+Assume $n\ge 2$ and fix $E$ and $E'$ as above.
+The any two sequences of elementary moves connecting $E$ to $E'$
+are related by a sequence of the two movie moves defined above.
+\end{lem}
+
+\begin{proof}
+(Sketch)
+Consider a two parameter family of diffeomorphisms (one parameter family of isotopies) 
+of $\bd X$.
+Up to homotopy,
+such a family is homotopic to a family which can be decomposed 
+into small families which are either
+(a) supported away from $E$, 
+(b) have boundaries corresponding to the two movie moves above.
+Finally, observe that the space of $E$'s is simply connected.
+(This fails for $n=1$.)
+\end{proof}
+
+For $n=1$ we have to check an additional ``global" relations corresponding to 
+rotating the 0-sphere $E$ around the 1-sphere $\bd X$.
+\nn{should check this global move, or maybe cite Frobenius reciprocity result}
+
 \nn{...}
 
 \medskip




