text/ncat.tex
changeset 858 1fc5fff34251
parent 857 4ad6325c7c7d
child 859 76a569bb2cec
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  2145 that our $n$-categories and modules have non-degenerate inner products.
  2145 that our $n$-categories and modules have non-degenerate inner products.
  2146 (In other words, we need to assume some extra duality on the $n$-categories and modules.)
  2146 (In other words, we need to assume some extra duality on the $n$-categories and modules.)
  2147 
  2147 
  2148 \medskip
  2148 \medskip
  2149 
  2149 
  2150 Our first task is to define an $n$-category $m$-sphere modules, for $0\le m \le n-1$.
  2150 Our first task is to define an $n$-category $m$-sphere module, for $0\le m \le n-1$.
  2151 These will be defined in terms of certain classes of marked balls, very similarly
  2151 These will be defined in terms of certain classes of marked balls, very similarly
  2152 to the definition of $n$-category modules above.
  2152 to the definition of $n$-category modules above.
  2153 (This, in turn, is very similar to our definition of $n$-category.)
  2153 (This, in turn, is very similar to our definition of $n$-category.)
  2154 Because of this similarity, we only sketch the definitions below.
  2154 Because of this similarity, we only sketch the definitions below.
  2155 
  2155 
  2390 The construction of the 0- through $n$-morphisms was easy and tautological, but the 
  2390 The construction of the 0- through $n$-morphisms was easy and tautological, but the 
  2391 $n{+}1$-morphisms will require some effort and combinatorial topology, as well as additional
  2391 $n{+}1$-morphisms will require some effort and combinatorial topology, as well as additional
  2392 duality assumptions on the lower morphisms. 
  2392 duality assumptions on the lower morphisms. 
  2393 These are required because we define the spaces of $n{+}1$-morphisms by 
  2393 These are required because we define the spaces of $n{+}1$-morphisms by 
  2394 making arbitrary choices of incoming and outgoing boundaries for each $n$-ball. 
  2394 making arbitrary choices of incoming and outgoing boundaries for each $n$-ball. 
  2395 The additional duality assumptions are needed to prove independence of our definition form these choices.
  2395 The additional duality assumptions are needed to prove independence of our definition from these choices.
  2396 
  2396 
  2397 Let $X$ be an $n{+}1$-ball, and let $c$ be a decoration of its boundary
  2397 Let $X$ be an $n{+}1$-ball, and let $c$ be a decoration of its boundary
  2398 by a cell complex labeled by 0- through $n$-morphisms, as above.
  2398 by a cell complex labeled by 0- through $n$-morphisms, as above.
  2399 Choose an $n{-}1$-sphere $E\sub \bd X$ which divides
  2399 Choose an $n{-}1$-sphere $E\sub \bd X$ which divides
  2400 $\bd X$ into ``incoming" and ``outgoing" boundary $\bd_-X$ and $\bd_+X$.
  2400 $\bd X$ into ``incoming" and ``outgoing" boundary $\bd_-X$ and $\bd_+X$.