diff -r 212991f176d1 -r 975c807661ca pnas/pnas.tex --- a/pnas/pnas.tex Wed Nov 17 15:24:09 2010 -0800 +++ b/pnas/pnas.tex Wed Nov 17 15:48:20 2010 -0800 @@ -215,16 +215,16 @@ We first give an account of our version of $n$-categories. According to our definition, $n$-categories are, among other things, functorial invariants of $k$-balls, $0\le k \le n$, which behave well with respect to gluing. -We then describe how to use [homotopy] colimits to extend $n$-categories -from balls to arbitrary $k$-manifolds. -This extension is the desired derived version of a TQFT, which we call the blob complex. +We then show how to extend an $n$-category from balls to arbitrary $k$-manifolds, +using colimits and homotopy colimits. +This extension, which we call the blob complex, has as $0$-th homology the usual TQFT invariant. (The name comes from the ``blobs" which feature prominently in a concrete version of the homotopy colimit.) We then review some basic properties of the blob complex, and finish by showing how it yields a higher categorical and higher dimensional generalization of Deligne's conjecture on Hochschild cochains and the little 2-disks operad. -\nn{maybe this is not necessary?} +\nn{maybe this is not necessary?} \nn{let's move this to somewhere later, if we keep it} In an attempt to forestall any confusion that might arise from different definitions of ``$n$-category" and ``TQFT", we note that our $n$-categories are both more and less general than the ``fully dualizable" ones which play a prominent role in \cite{0905.0465}. @@ -233,13 +233,7 @@ Thus our $n$-categories correspond to $(n{+}\epsilon)$-dimensional unoriented or oriented TQFTs, while Lurie's (fully dualizable) $n$-categories correspond to $(n{+}1)$-dimensional framed TQFTs. -Details missing from this paper can usually be found in \cite{1009.5025}. - -%\nn{In many places we omit details; they can be found in MW. -%(Blanket statement in order to avoid too many citations to MW.)} -% -%\nn{perhaps say something explicit about the relationship of this paper to big blob paper. -%like: in this paper we try to give a clear view of the big picture without getting bogged down in details} +At several points we only sketch an argument briefly; full details can be found in \cite{1009.5025}. In this paper we attempt to give a clear view of the big picture without getting bogged down in technical details. \section{Definitions} @@ -290,15 +284,13 @@ to the standard $k$-ball $B^k$. \nn{maybe add that in addition we want functoriality} -We haven't said precisely what sort of balls we are considering, -because we prefer to let this detail be a parameter in the definition. -It is useful to consider unoriented, oriented, Spin and $\mbox{Pin}_\pm$ balls. -Also useful are more exotic structures, such as balls equipped with a map to some target space, +By default our balls are oriented, +but it is useful at times to vary this, +for example by considering unoriented or Spin balls. +We can also consider more exotic structures, such as balls with a map to some target space, or equipped with $m$ independent vector fields. (The latter structure would model $n$-categories with less duality than we usually assume.) -%In fact, the axioms here may easily be varied by considering balls with structure (e.g. $m$ independent vector fields, a map to some target space, etc.). Such variations are useful for axiomatizing categories with less duality, and also as technical tools in proofs. - \begin{axiom}[Morphisms] \label{axiom:morphisms} For each $0 \le k \le n$, we have a functor $\cC_k$ from