diff -r 5bb1cbe49c40 -r ef8fac44a8aa text/intro.tex --- a/text/intro.tex Mon May 31 17:27:17 2010 -0700 +++ b/text/intro.tex Mon May 31 23:42:37 2010 -0700 @@ -26,15 +26,18 @@ Nevertheless, when we attempt to establish all of the observed properties of the blob complex, we find this situation unsatisfactory. Thus, in the second part of the paper (section \S \ref{sec:ncats}) we pause and give yet another definition of an $n$-category, or rather a definition of an $n$-category with strong duality. (It appears that removing the duality conditions from our definition would make it more complicated rather than less.) We call these ``topological $n$-categories'', to differentiate them from previous versions. Moreover, we find that we need analogous $A_\infty$ $n$-categories, and we define these as well following very similar axioms. -The basic idea is that each potential definition of an $n$-category makes a choice about the `shape' of morphisms. We try to be as lax as possible: a topological $n$-category associates a vector space to every $B$ homeomorphic to the $n$-ball. These vector spaces glue together associatively, and we require that there is an action of the homeomorphism group. +The basic idea is that each potential definition of an $n$-category makes a choice about the `shape' of morphisms. We try to be as lax as possible: a topological $n$-category associates a vector space to every $B$ homeomorphic to the $n$-ball. These vector spaces glue together associatively, and we require that there is an action of the homeomorphism groupoid. For an $A_\infty$ $n$-category, we associate a chain complex instead of a vector space to each such $B$ and ask that the action of homeomorphisms extends to a suitably defined action of the complex of singular chains of homeomorphisms. The axioms for an $A_\infty$ $n$-category are designed to capture two main examples: the blob complexes of $n$-balls labelled by a topological $n$-category, and the complex $\CM{-}{T}$ of maps to a fixed target space $T$. -In \S \ref{sec:ainfblob} we explain how to construct a system of fields from a topological $n$-category, and give an alternative definition of the blob complex for an $A_\infty$ $n$-category on an $n$-manifold. Using these definitions, we show how to use the blob complex to `resolve' any topological $n$-category as an $A_\infty$ $n$-category, and relate the first and second definitions of the blob complex. We use the blob complex for $A_\infty$ $n$-categories to establish important properties of the blob complex (in both variants), in particular the `gluing formula' of Property \ref{property:gluing} below. +In \S \ref{sec:ainfblob} we explain how to construct a system of fields from a topological $n$-category (using a colimit along cellulations of a manifold), and give an alternative definition of the blob complex for an $A_\infty$ $n$-category on an $n$-manifold (analogously, using a homotopy colimit). Using these definitions, we show how to use the blob complex to `resolve' any topological $n$-category as an $A_\infty$ $n$-category, and relate the first and second definitions of the blob complex. We use the blob complex for $A_\infty$ $n$-categories to establish important properties of the blob complex (in both variants), in particular the `gluing formula' of Property \ref{property:gluing} below. + +The relationship between all these ideas is sketched in Figure \ref{fig:outline}. \nn{KW: the previous two paragraphs seem a little awkward to me, but I don't presently have a good idea for fixing them.} \tikzstyle{box} = [rectangle, rounded corners, draw,outer sep = 5pt, inner sep = 5pt, line width=0.5pt] +\begin{figure}[!ht] {\center \begin{tikzpicture}[align=center,line width = 1.5pt] @@ -69,6 +72,9 @@ \end{tikzpicture} } +\caption{The main gadgets and constructions of the paper.} +\label{fig:outline} +\end{figure} Finally, later sections address other topics. Section \S \ref{sec:comm_alg} describes the blob complex when $\cC$ is a commutative algebra, thought of as a topological $n$-category, in terms of the topology of $M$. Section \S \ref{sec:deligne} states (and in a later edition of this paper, hopefully proves) a higher dimensional generalization of the Deligne conjecture (that the little discs operad acts on Hochschild cohomology) in terms of the blob complex. The appendixes prove technical results about $\CH{M}$, and make connections between our definitions of $n$-categories and familiar definitions for $n=1$ and $n=2$, as well as relating the $n=1$ case of our $A_\infty$ $n$-categories with usual $A_\infty$ algebras. @@ -167,7 +173,7 @@ \end{property} As a consequence, there is an action of $\Homeo(X)$ on the chain complex $\bc_*^\cC(X)$; this action is extended to all of $C_*(\Homeo(X))$ in Property \ref{property:evaluation} below. -The blob complex is also functorial with respect to $\cC$, although we will not address this in detail here. \todo{exact w.r.t $\cC$?} +The blob complex is also functorial (indeed, exact) with respect to $\cC$, although we will not address this in detail here. \begin{property}[Disjoint union] \label{property:disjoint-union} @@ -220,19 +226,20 @@ \end{property} In the following $\CH{X}$ is the singular chain complex of the space of homeomorphisms of $X$, fixed on $\bdy X$. -\begin{property}[$C_*(\Homeo(-))$ action] +\begin{property}[$C_*(\Homeo(-))$ action]\mbox{}\\ +\vspace{-0.5cm} \label{property:evaluation}% -There is a chain map +\begin{enumerate} +\item There is a chain map \begin{equation*} \ev_X: \CH{X} \tensor \bc_*(X) \to \bc_*(X). \end{equation*} -Restricted to $C_0(\Homeo(X))$ this is just the action of homeomorphisms described in Property \ref{property:functoriality}. -\nn{should probably say something about associativity here (or not?)} +\item Restricted to $C_0(\Homeo(X))$ this is the action of homeomorphisms described in Property \ref{property:functoriality}. -For +\item For any codimension $0$-submanifold $Y \sqcup Y^\text{op} \subset \bdy X$ the following diagram -(using the gluing maps described in Property \ref{property:gluing-map}) commutes. +(using the gluing maps described in Property \ref{property:gluing-map}) commutes (up to homotopy). \begin{equation*} \xymatrix@C+2cm{ \CH{X \bigcup_Y \selfarrow} \otimes \bc_*(X \bigcup_Y \selfarrow) \ar[r]^<<<<<<<<<<<<{\ev_{(X \bigcup_Y \scalebox{0.5}{\selfarrow})}} & \bc_*(X \bigcup_Y \selfarrow) \\ @@ -241,15 +248,23 @@ \bc_*(X) \ar[u]_{\gl_Y} } \end{equation*} - -\nn{unique up to homotopy?} +\item Any such chain map satisfying points 2. and 3. above is unique, up to an iterated homotopy. (That is, any pair of homotopies have a homotopy between them, and so on.) +\item This map is associative, in the sense that the following diagram commutes (up to homotopy). +\begin{equation*} +\xymatrix{ +\CH{X} \tensor \CH{X} \tensor \bc_*(X) \ar[r]^<<<<<{\id \tensor \ev_X} \ar[d]^{\compose \tensor \id} & \CH{X} \tensor \bc_*(X) \ar[d]^{\ev_X} \\ +\CH{X} \tensor \bc_*(X) \ar[r]^{\ev_X} & \bc_*(X) +} +\end{equation*} +\end{enumerate} \end{property} -Since the blob complex is functorial in the manifold $X$, we can use this to build a chain map +Since the blob complex is functorial in the manifold $X$, this is equivalent to having chain maps $$ev_{X \to Y} : \CH{X \to Y} \tensor \bc_*(X) \to \bc_*(Y)$$ +for any homeomorphic pair $X$ and $Y$, satisfying corresponding conditions. -In \S \ref{sec:ncats} we introduce the notion of topological $n$-categories, from which we can construct systems of fields. Below, we talk about the blob complex associated to a topological $n$-category, implicitly passing to the system of fields. Further, in \S \ref{sec:ncats} we also have the notion of an $A_\infty$ $n$-category. +In \S \ref{sec:ncats} we introduce the notion of topological $n$-categories, from which we can construct systems of fields. Below, we talk about the blob complex associated to a topological $n$-category, implicitly passing first to the system of fields. Further, in \S \ref{sec:ncats} we also have the notion of an $A_\infty$ $n$-category. \begin{property}[Blob complexes of (products with) balls form an $A_\infty$ $n$-category] \label{property:blobs-ainfty}