text/intro.tex
changeset 464 6c760675d461
parent 454 3377d4db80d9
child 481 7caafccef7e8
equal deleted inserted replaced
463:982eca6e2663 464:6c760675d461
    57 homeomorphisms extends to a suitably defined action of the complex of singular chains of homeomorphisms.
    57 homeomorphisms extends to a suitably defined action of the complex of singular chains of homeomorphisms.
    58 The axioms for an $A_\infty$ $n$-category are designed to capture two main examples: the blob complexes of $n$-balls labelled by a 
    58 The axioms for an $A_\infty$ $n$-category are designed to capture two main examples: the blob complexes of $n$-balls labelled by a 
    59 topological $n$-category, and the complex $\CM{-}{T}$ of maps to a fixed target space $T$.
    59 topological $n$-category, and the complex $\CM{-}{T}$ of maps to a fixed target space $T$.
    60 
    60 
    61 In \S \ref{ss:ncat_fields}  we explain how to construct a system of fields from a topological $n$-category 
    61 In \S \ref{ss:ncat_fields}  we explain how to construct a system of fields from a topological $n$-category 
    62 (using a colimit along cellulations of a manifold), and in \S \ref{sec:ainfblob} give an alternative definition 
    62 (using a colimit along certain decompositions of a manifold into balls). With this in hand, we freely write $\bc_*(M; \cC)$ to indicate the blob complex of a manifold $M$ with the system of fields constructed from the $n$-category $\cC$. In \S \ref{sec:ainfblob} we give an alternative definition 
    63 of the blob complex for an $A_\infty$ $n$-category on an $n$-manifold (analogously, using a homotopy colimit).
    63 of the blob complex for an $A_\infty$ $n$-category on an $n$-manifold (analogously, using a homotopy colimit).
    64 Using these definitions, we show how to use the blob complex to ``resolve" any topological $n$-category as an 
    64 Using these definitions, we show how to use the blob complex to ``resolve" any topological $n$-category as an 
    65 $A_\infty$ $n$-category, and relate the first and second definitions of the blob complex.
    65 $A_\infty$ $n$-category, and relate the first and second definitions of the blob complex.
    66 We use the blob complex for $A_\infty$ $n$-categories to establish important properties of the blob complex (in both variants), 
    66 We use the blob complex for $A_\infty$ $n$-categories to establish important properties of the blob complex (in both variants), 
    67 in particular the ``gluing formula" of Theorem \ref{thm:gluing} below.
    67 in particular the ``gluing formula" of Theorem \ref{thm:gluing} below.
   205 
   205 
   206 \begin{property}[Functoriality]
   206 \begin{property}[Functoriality]
   207 \label{property:functoriality}%
   207 \label{property:functoriality}%
   208 The blob complex is functorial with respect to homeomorphisms.
   208 The blob complex is functorial with respect to homeomorphisms.
   209 That is, 
   209 That is, 
   210 for a fixed $n$-dimensional system of fields $\cC$, the association
   210 for a fixed $n$-dimensional system of fields $\cF$, the association
   211 \begin{equation*}
   211 \begin{equation*}
   212 X \mapsto \bc_*(X; \cC)
   212 X \mapsto \bc_*(X; \cF)
   213 \end{equation*}
   213 \end{equation*}
   214 is a functor from $n$-manifolds and homeomorphisms between them to chain 
   214 is a functor from $n$-manifolds and homeomorphisms between them to chain 
   215 complexes and isomorphisms between them.
   215 complexes and isomorphisms between them.
   216 \end{property}
   216 \end{property}
   217 As a consequence, there is an action of $\Homeo(X)$ on the chain complex $\bc_*(X; \cC)$; 
   217 As a consequence, there is an action of $\Homeo(X)$ on the chain complex $\bc_*(X; \cF)$; 
   218 this action is extended to all of $C_*(\Homeo(X))$ in Theorem \ref{thm:evaluation} below.
   218 this action is extended to all of $C_*(\Homeo(X))$ in Theorem \ref{thm:evaluation} below.
   219 
   219 
   220 The blob complex is also functorial (indeed, exact) with respect to $\cC$, 
   220 The blob complex is also functorial (indeed, exact) with respect to $\cF$, 
   221 although we will not address this in detail here.
   221 although we will not address this in detail here.
   222 
   222 
   223 \begin{property}[Disjoint union]
   223 \begin{property}[Disjoint union]
   224 \label{property:disjoint-union}
   224 \label{property:disjoint-union}
   225 The blob complex of a disjoint union is naturally the tensor product of the blob complexes.
   225 The blob complex of a disjoint union is naturally the tensor product of the blob complexes.
   246 \end{property}
   246 \end{property}
   247 
   247 
   248 \begin{property}[Contractibility]
   248 \begin{property}[Contractibility]
   249 \label{property:contractibility}%
   249 \label{property:contractibility}%
   250 With field coefficients, the blob complex on an $n$-ball is contractible in the sense that it is homotopic to its $0$-th homology.
   250 With field coefficients, the blob complex on an $n$-ball is contractible in the sense that it is homotopic to its $0$-th homology.
   251 Moreover, the $0$-th homology of balls can be canonically identified with the vector spaces associated by the system of fields $\cC$ to balls.
   251 Moreover, the $0$-th homology of balls can be canonically identified with the vector spaces associated by the system of fields $\cF$ to balls.
   252 \begin{equation*}
   252 \begin{equation*}
   253 \xymatrix{\bc_*(B^n;\cC) \ar[r]^(0.4){\iso}_(0.4){\text{qi}} & H_0(\bc_*(B^n;\cC)) \ar[r]^(0.6)\iso & \cC(B^n)}
   253 \xymatrix{\bc_*(B^n;\cF) \ar[r]^(0.4){\iso}_(0.4){\text{qi}} & H_0(\bc_*(B^n;\cF)) \ar[r]^(0.6)\iso & \cF(B^n)}
   254 \end{equation*}
   254 \end{equation*}
   255 \end{property}
   255 \end{property}
   256 
   256 
   257 Properties \ref{property:functoriality} will be immediate from the definition given in
   257 Properties \ref{property:functoriality} will be immediate from the definition given in
   258 \S \ref{sec:blob-definition}, and we'll recall it at the appropriate point there.
   258 \S \ref{sec:blob-definition}, and we'll recall it at the appropriate point there.
   266 \newtheorem*{thm:skein-modules}{Theorem \ref{thm:skein-modules}}
   266 \newtheorem*{thm:skein-modules}{Theorem \ref{thm:skein-modules}}
   267 
   267 
   268 \begin{thm:skein-modules}[Skein modules]
   268 \begin{thm:skein-modules}[Skein modules]
   269 The $0$-th blob homology of $X$ is the usual 
   269 The $0$-th blob homology of $X$ is the usual 
   270 (dual) TQFT Hilbert space (a.k.a.\ skein module) associated to $X$
   270 (dual) TQFT Hilbert space (a.k.a.\ skein module) associated to $X$
   271 by $\cC$.
   271 by $\cF$.
   272 (See \S \ref{sec:local-relations}.)
   272 (See \S \ref{sec:local-relations}.)
   273 \begin{equation*}
   273 \begin{equation*}
   274 H_0(\bc_*(X;\cC)) \iso A_{\cC}(X)
   274 H_0(\bc_*(X;\cF)) \iso A_{\cF}(X)
   275 \end{equation*}
   275 \end{equation*}
   276 \end{thm:skein-modules}
   276 \end{thm:skein-modules}
   277 
   277 
   278 \newtheorem*{thm:hochschild}{Theorem \ref{thm:hochschild}}
   278 \newtheorem*{thm:hochschild}{Theorem \ref{thm:hochschild}}
   279 
   279 
   467 Kevin Costello, 
   467 Kevin Costello, 
   468 Chris Douglas,
   468 Chris Douglas,
   469 and
   469 and
   470 Alexander Kirillov
   470 Alexander Kirillov
   471 for many interesting and useful conversations. 
   471 for many interesting and useful conversations. 
   472 During this work, Kevin Walker has been at Microsoft Station Q, and Scott Morrison has been at Microsoft Station Q and the Miller Institute for Basic Research at UC Berkeley.
   472 During this work, Kevin Walker has been at Microsoft Station Q, and Scott Morrison has been at Microsoft Station Q and the Miller Institute for Basic Research at UC Berkeley. We'd like to thank the Aspen Center for Physics for the conducive environment provided there during the final preparation of this manuscript.
   473 
   473