blob1.tex
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parent 22 ada83e7228eb
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   227 
   227 
   228 A {\it system of fields}
   228 A {\it system of fields}
   229 \nn{maybe should look for better name; but this is the name I use elsewhere}
   229 \nn{maybe should look for better name; but this is the name I use elsewhere}
   230 is a collection of functors $\cC$ from manifolds of dimension $n$ or less
   230 is a collection of functors $\cC$ from manifolds of dimension $n$ or less
   231 to sets.
   231 to sets.
   232 These functors must satisfy various properties (see KW TQFT notes for details).
   232 These functors must satisfy various properties (see \cite{kw:tqft} for details).
   233 For example:
   233 For example:
   234 there is a canonical identification $\cC(X \du Y) = \cC(X) \times \cC(Y)$;
   234 there is a canonical identification $\cC(X \du Y) = \cC(X) \times \cC(Y)$;
   235 there is a restriction map $\cC(X) \to \cC(\bd X)$;
   235 there is a restriction map $\cC(X) \to \cC(\bd X)$;
   236 gluing manifolds corresponds to fibered products of fields;
   236 gluing manifolds corresponds to fibered products of fields;
   237 given a field $c \in \cC(Y)$ there is a ``product field"
   237 given a field $c \in \cC(Y)$ there is a ``product field"
   379 (for all $c \in \cC(\bd B^n)$) satisfying the following (three?) properties.
   379 (for all $c \in \cC(\bd B^n)$) satisfying the following (three?) properties.
   380 
   380 
   381 \nn{Roughly, these are (1) the local relations imply (extended) isotopy;
   381 \nn{Roughly, these are (1) the local relations imply (extended) isotopy;
   382 (2) $U(B^n; \cdot)$ is an ideal w.r.t.\ gluing; and
   382 (2) $U(B^n; \cdot)$ is an ideal w.r.t.\ gluing; and
   383 (3) this ideal is generated by ``small" generators (contained in an open cover of $B^n$).
   383 (3) this ideal is generated by ``small" generators (contained in an open cover of $B^n$).
   384 See KW TQFT notes for details.  Need to transfer details to here.}
   384 See \cite{kw:tqft} for details.  Need to transfer details to here.}
   385 
   385 
   386 For maps into spaces, $U(B^n; c)$ is generated by things of the form $a-b \in \cC_l(B^n; c)$,
   386 For maps into spaces, $U(B^n; c)$ is generated by things of the form $a-b \in \cC_l(B^n; c)$,
   387 where $a$ and $b$ are maps (fields) which are homotopic rel boundary.
   387 where $a$ and $b$ are maps (fields) which are homotopic rel boundary.
   388 
   388 
   389 For $n$-category pictures, $U(B^n; c)$ is equal to the kernel of the evaluation map
   389 For $n$-category pictures, $U(B^n; c)$ is equal to the kernel of the evaluation map
   401 Given a system of fields and local relations, we define the skein space
   401 Given a system of fields and local relations, we define the skein space
   402 $A(Y^n; c)$ to be the space of all finite linear combinations of fields on
   402 $A(Y^n; c)$ to be the space of all finite linear combinations of fields on
   403 the $n$-manifold $Y$ modulo local relations.
   403 the $n$-manifold $Y$ modulo local relations.
   404 The Hilbert space $Z(Y; c)$ for the TQFT based on the fields and local relations
   404 The Hilbert space $Z(Y; c)$ for the TQFT based on the fields and local relations
   405 is defined to be the dual of $A(Y; c)$.
   405 is defined to be the dual of $A(Y; c)$.
   406 (See KW TQFT notes or xxxx for details.)
   406 (See \cite{kw:tqft} or xxxx for details.)
   407 
   407 
   408 The blob complex is in some sense the derived version of $A(Y; c)$.
   408 The blob complex is in some sense the derived version of $A(Y; c)$.
   409 
   409 
   410 
   410 
   411 
   411 
   916 \label{sec:gluing}%
   916 \label{sec:gluing}%
   917 
   917 
   918 \subsection{`Topological' $A_\infty$ $n$-categories}
   918 \subsection{`Topological' $A_\infty$ $n$-categories}
   919 \label{sec:topological-A-infty}%
   919 \label{sec:topological-A-infty}%
   920 
   920 
   921 This section prepares the ground for establishing Property \ref{property:gluing} by defining the notion of a \emph{topological $A_\infty$
   921 This section prepares the ground for establishing Property \ref{property:gluing} by defining the notion of a \emph{topological $A_\infty$-$n$-category}.
   922 $n$-category}. The main result of this section is
   922 The main result of this section is
   923 
   923 
   924 \begin{thm}
   924 \begin{thm}
   925 Topological $A_\infty$ $1$-categories are equivalent to `standard'
   925 Topological $A_\infty$-$1$-categories are equivalent to `standard'
   926 $A_\infty$ $1$-categories.
   926 $A_\infty$-$1$-categories.
   927 \end{thm}
   927 \end{thm}
   928 
   928 
   929 
   929 Before proving this theorem, we embark upon a long string of definitions. For expository purposes, we begin with the $n=1$ special cases, and define
       
   930 first topological $A_\infty$-algebras, then topological $A_\infty$-categories, and then topological $A_\infty$-modules over these. We then turn
       
   931 to the general $n$ case, defining topological $A_\infty$-$n$-categories and their modules.
       
   932 \nn{Something about duals?}
       
   933 \todo{Explain that we're not making contact with any previous notions for the general $n$ case?}
       
   934 
       
   935 \begin{defn}
       
   936 \label{defn:topological-algebra}%
       
   937 A ``topological $A_\infty$-algebra'' $A$ consists of the data
       
   938 \begin{enumerate}
       
   939 \item for each $1$-manifold $J$ diffeomorphic to the standard interval $I=\left[0,1\right]$, a complex of vector spaces $A(J)$,
       
   940 \item along with an `evaluation' chain map $\ev_J : \CD{J} \tensor A(J) \to A(J)$,
       
   941 \item for each diffeomorphism $\phi : J \to J'$, an isomorphism $A(\phi) : A(J) \isoto A(J')$,
       
   942 \item and whenever $\bdy J \cap \bdy J'$ is a single point, a gluing map $\gl_{J,J'} : A(J) \tensor A(J') \to A(J \cup J')$,
       
   943 \end{enumerate}
       
   944 satisfying the following conditions.
       
   945 \begin{itemize}
       
   946 \item If $\phi$ is a diffeomorphism from $J$ to itself, the maps $\ev_J(\phi, -)$ and $A(\phi)$ are the same.
       
   947 \item The evaluation chain map is associative, in that the diagram
       
   948 \begin{equation*}
       
   949 \xymatrix{
       
   950 \CD{J} \tensor \CD{J} \tensor A(J) \ar[r]^{\Id \tensor \ev_J} \ar[d]_{\compose \tensor \Id} &
       
   951 \CD{J} \tensor A(J) \ar[d]^{\ev_J} \\
       
   952 \CD{J} \tensor A(J) \ar[r]_{\ev_J} &
       
   953 A(J)
       
   954 }
       
   955 \end{equation*}
       
   956 commutes. (Here the map $\compose : \CD{J} \tensor \CD{J} \to \CD{J}$ is a composition: take products of singular chains first, then use the group multiplication in $\Diff(J)$.)
       
   957 \item The gluing maps are \emph{strictly} associative. That is, given $J$, $J'$ and $J''$, the diagram
       
   958 \begin{equation*}
       
   959 \xymatrix{
       
   960 A(J) \tensor A(J') \tensor A(J'') \ar[rr]^{\gl_{J,J'} \tensor \Id} \ar[d]_{\Id \tensor \gl_{J',J''}} &&
       
   961 A(J \cup J') \tensor A(J'') \ar[d]^{\gl_{J \cup J', J''}} \\
       
   962 A(J) \tensor A(J' \cup J'') \ar[rr]_{\gl_{J, J' \cup J''}} &&
       
   963 A(J \cup J' \cup J'')
       
   964 }
       
   965 \end{equation*}
       
   966 commutes.
       
   967 \end{itemize}
       
   968 \end{defn}
       
   969 
       
   970 \begin{rem}
       
   971 Of course, the first and third pieces of data (the complexes, and the isomorphisms) together just constitute a functor from the category of
       
   972 intervals and diffeomorphisms between them to the category of complexes of vector spaces.
       
   973 Further, one can combine the second and third pieces of data, asking instead for a map
       
   974 \begin{equation*}
       
   975 \ev_{J,J'} : \CD{J \to J'} \tensor A(J) \to A(J').
       
   976 \end{equation*}
       
   977 (Any $k$-parameter family of diffeomorphisms in $C_k(\Diff(J \to J'))$ factors into a single diffeomorphism $J \to J'$ and a $k$-parameter family of
       
   978 diffeomorphisms in $\CD{J'}$.)
       
   979 \end{rem}
       
   980 
       
   981 To generalise the definition to that of a category, we simply introduce a set of objects which we call $A(pt)$. Now we associate complexes to each
       
   982 interval with boundary conditions $(J, c_-, c_+)$, with $c_-, c_+ \in A(pt)$, and only ask for gluing maps when the boundary conditions match up:
       
   983 \begin{equation*}
       
   984 \gl : A(J, c_-, c_0) \tensor A(J', c_0, c_+) \to A(J \cup J', c_-, c_+).
       
   985 \end{equation*}
       
   986 The action of diffeomorphisms, and $k$-parameter families of diffeomorphisms, ignore the boundary conditions.
       
   987 
       
   988 The definition of a module follows closely the definition of an algebra or category.
       
   989 \begin{defn}
       
   990 \label{defn:topological-module}%
       
   991 A topological $A_\infty$-(left-)module $M$ over a topological $A_\infty$ category $A$ consists of the data
       
   992 \begin{enumerate}
       
   993 \item a functor $K \mapsto M(K)$ from $1$-manifolds diffeomorphic to the standard interval, with a marked point on a boundary, to complexes of vector spaces,
       
   994 \item along with an `evaluation' map $\ev_K : \CD{K} \tensor M(K) \to M(K)$
       
   995 \item whenever $\bdy J \cap K$ is a single point, and isn't the marked point of $K$ \todo{ugh, that's so gross}, a gluing map
       
   996 $\gl_{J,K} : A(J) \tensor M(K) \to M(J \cup K)$
       
   997 \end{enumerate}
       
   998 satisfying the obvious analogous conditions as in Definition \ref{defn:topological-algebra}.
       
   999 \end{defn}
       
  1000 
       
  1001 \todo{Bimodules, and gluing}
       
  1002 
       
  1003 \todo{the motivating example $C_*(\maps(X, M))$}
       
  1004 
       
  1005 \todo{higher $n$}
       
  1006 
       
  1007 
       
  1008 \newcommand{\skel}[1]{\operatorname{skeleton}(#1)}
       
  1009 
       
  1010 Given a topological $A_\infty$-category $\cC$, we can construct an `algebraic' $A_\infty$ category $\skel{\cC}$. First, pick your
       
  1011 favorite diffeomorphism $\phi: I \cup I \to I$.
       
  1012 \begin{defn}
       
  1013 We'll write $\skel{\cC} = (A, m_k)$. Define $A = \cC(I)$, and $m_2 : A \tensor A \to A$ by
       
  1014 \begin{equation*}
       
  1015 m_2 \cC(I) \tensor \cC(I) \xrightarrow{\gl_{I,I}} \cC(I \cup I) \xrightarrow{\cC(\phi)} \cC(I).
       
  1016 \end{equation*}
       
  1017 Next, we define all the `higher associators' $m_k$ by
       
  1018 \todo{}
       
  1019 \end{defn}
       
  1020 
       
  1021 Give an `algebraic' $A_\infty$ category $(A, m_k)$, we can construct a topological $A_\infty$-category, which we call $\bc_*^A$. You should
       
  1022 think of this at the generalisation of the blob complex, although the construction we give will \emph{not} specialise to exactly the usual definition
       
  1023 in the case the $A$ is actually an associative category.
       
  1024 \begin{defn}
       
  1025 \end{defn}
   930 
  1026 
   931 \nn{Need to let the input $n$-category $C$ be a graded thing (e.g. DG
  1027 \nn{Need to let the input $n$-category $C$ be a graded thing (e.g. DG
   932 $n$-category or $A_\infty$ $n$-category). DG $n$-category case is pretty
  1028 $n$-category or $A_\infty$ $n$-category). DG $n$-category case is pretty
   933 easy, I think, so maybe it should be done earlier??}
  1029 easy, I think, so maybe it should be done earlier??}
   934 
  1030 
  1194 \nn{this completes proof}
  1290 \nn{this completes proof}
  1195 
  1291 
  1196 \input{text/explicit.tex}
  1292 \input{text/explicit.tex}
  1197 
  1293 
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