# HG changeset patch # User Scott Morrison # Date 1317773528 25200 # Node ID 9ba67422f1b9feb07138acbb4f0e485ae08b6129 # Parent deeff619087eee05aaaf9a0cfbef37d4b60062e0 minor fixes, some typos, some cross-references diff -r deeff619087e -r 9ba67422f1b9 RefereeReport.pdf Binary file RefereeReport.pdf has changed diff -r deeff619087e -r 9ba67422f1b9 text/ncat.tex --- a/text/ncat.tex Mon Oct 03 16:40:16 2011 -0700 +++ b/text/ncat.tex Tue Oct 04 17:12:08 2011 -0700 @@ -582,6 +582,7 @@ even when we reparametrize our $n$-balls. \begin{axiom}[\textup{\textbf{[preliminary]}} Isotopy invariance in dimension $n$] +\label{axiom:isotopy-preliminary} Let $X$ be an $n$-ball, $b \in \cC(X)$, and $f: X\to X$ be a homeomorphism which acts trivially on the restriction $\bd b$ of $b$ to $\bd X$. (Keep in mind the important special case where $f$ restricted to $\bd X$ is the identity.) @@ -679,7 +680,7 @@ nevertheless we feel that it is too strong. In the future we would like to see this provisional version of the axiom replaced by something less restrictive. -We give two alternate versions of he axiom, one better suited for smooth examples, and one better suited to PL examples. +We give two alternate versions of the axiom, one better suited for smooth examples, and one better suited to PL examples. \begin{axiom}[Splittings] \label{axiom:splittings} @@ -1003,7 +1004,7 @@ Once we have the above $n$-category axioms for $n{-}1$-morphisms, we can define the category $\bbc$ of {\it $n$-balls with boundary conditions}. Its objects are pairs $(X, c)$, where $X$ is an $n$-ball and $c \in \cl\cC(\bd X)$ is the ``boundary condition". -The morphisms from $(X, c)$ to $(X', c')$, denoted $\Homeo(X,c; X', c')$, are +The morphisms from $(X, c)$ to $(X', c')$, denoted $\Homeo(X; c \to X'; c')$, are homeomorphisms $f:X\to X'$ such that $f|_{\bd X}(c) = c'$. %Let $\pi_0(\bbc)$ denote @@ -1047,7 +1048,7 @@ } Recall the category $\bbc$ of balls with boundary conditions. -Note that the morphisms $\Homeo(X,c; X', c')$ from $(X, c)$ to $(X', c')$ form a topological space. +Note that the morphisms $\Homeo(X;c \to X'; c')$ from $(X, c)$ to $(X', c')$ form a topological space. Let $\cS$ be an appropriate $\infty$-category (e.g.\ chain complexes) and let $\cJ$ be an $\infty$-functor from topological spaces to $\cS$ (e.g.\ the singular chain functor $C_*$). @@ -1056,7 +1057,7 @@ \label{axiom:families} For each pair of $n$-balls $X$ and $X'$ and each pair $c\in \cl{\cC}(\bd X)$ and $c'\in \cl{\cC}(\bd X')$ we have an $\cS$-morphism \[ - \cJ(\Homeo(X,c; X', c')) \ot \cC(X; c) \to \cC(X'; c') . + \cJ(\Homeo(X;c \to X'; c')) \ot \cC(X; c) \to \cC(X'; c') . \] Similarly, we have an $\cS$-morphism \[ @@ -1071,7 +1072,7 @@ \end{axiom} We now describe the topology on $\Coll(X; c)$. -We retain notation from the above definition of collar map. +We retain notation from the above definition of collar map (after Axiom \ref{axiom:isotopy-preliminary}). Each collaring homeomorphism $X \cup (Y\times J) \to X$ determines a map from points $p$ of $\bd X$ to (possibly length zero) embedded intervals in $X$ terminating at $p$. If $p \in Y$ this interval is the image of $\{p\}\times J$. @@ -1082,14 +1083,14 @@ maps follows from the action of families of homeomorphisms and compatibility with gluing.) The $k=n$ case of Axiom \ref{axiom:morphisms} posits a {\it strictly} associative action of {\it sets} -$\Homeo(X,c; X', c') \times \cC(X; c) \to \cC(X'; c')$, and at first it might seem that this would force the above -action of $\cJ(\Homeo(X,c; X', c'))$ to be strictly associative as well (assuming the two actions are compatible). +$\Homeo(X;c\to X'; c') \times \cC(X; c) \to \cC(X'; c')$, and at first it might seem that this would force the above +action of $\cJ(\Homeo(X;c\to X'; c'))$ to be strictly associative as well (assuming the two actions are compatible). In fact, compatibility implies less than this. For simplicity, assume that $\cJ$ is $C_*$, the singular chains functor. (This is the example most relevant to this paper.) -Then compatibility implies that the action of $C_*(\Homeo(X,c; X', c'))$ agrees with the action -of $C_0(\Homeo(X,c; X', c'))$ coming from Axiom \ref{axiom:morphisms}, so we only require associativity in degree zero. -And indeed, this is true for our main example of an $A_\infty$ $n$-category based on the blob construction. +Then compatibility implies that the action of $C_*(\Homeo(X;c\to X'; c'))$ agrees with the action +of $C_0(\Homeo(X;c\to X'; c'))$ coming from Axiom \ref{axiom:morphisms}, so we only require associativity in degree zero. +And indeed, this is true for our main example of an $A_\infty$ $n$-category based on the blob construction (see Example \ref{ex:blob-complexes-of-balls} below). Stating this sort of compatibility for general $\cS$ and $\cJ$ requires further assumptions, such as the forgetful functor from $\cS$ to sets having a left adjoint, and $\cS$ having an internal Hom. @@ -1142,7 +1143,7 @@ invariance in dimension $n$, while in the fields definition we instead remember a subspace of local relations which contain differences of isotopic fields. (Recall that the compensation for this complication is that we can demand that the gluing map for fields is injective.) -Thus a system of fields and local relations $(\cF,U)$ determines an $n$-category $\cC_ {\cF,U}$ simply by restricting our attention to +Thus a \nn{lemma-ize} system of fields and local relations $(\cF,U)$ determines an $n$-category $\cC_ {\cF,U}$ simply by restricting our attention to balls and, at level $n$, quotienting out by the local relations: \begin{align*} \cC_{\cF,U}(B^k) & = \begin{cases}\cF(B) & \text{when $k