text/hochschild.tex
changeset 940 04079a7aeaef
parent 894 3f38383f26d3
child 961 c57afb230bb1
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   210 We claim that $J_*$ is homotopy equivalent to $\bc_*(S^1)$.
   210 We claim that $J_*$ is homotopy equivalent to $\bc_*(S^1)$.
   211 Let $F_*^\ep \sub \bc_*(S^1)$ be the subcomplex where either
   211 Let $F_*^\ep \sub \bc_*(S^1)$ be the subcomplex where either
   212 (a) the point * is not on the boundary of any blob or
   212 (a) the point * is not on the boundary of any blob or
   213 (b) there are no labeled points or blob boundaries within distance $\ep$ of *,
   213 (b) there are no labeled points or blob boundaries within distance $\ep$ of *,
   214 other than blob boundaries at * itself.
   214 other than blob boundaries at * itself.
   215 Note that all blob diagrams are in $F_*^\ep$ for $\ep$ sufficiently small.
   215 Note that all blob diagrams are in some $F_*^\ep$ for $\ep$ sufficiently small.
   216 Let $b$ be a blob diagram in $F_*^\ep$.
   216 Let $b$ be a blob diagram in $F_*^\ep$.
   217 Define $f(b)$ to be the result of moving any blob boundary points which lie on *
   217 Define $f(b)$ to be the result of moving any blob boundary points which lie on *
   218 to distance $\ep$ from *.
   218 to distance $\ep$ from *.
   219 (Move right or left so as to shrink the blob.)
   219 (Move right or left so as to shrink the blob.)
   220 Extend to get a chain map $f: F_*^\ep \to F_*^\ep$.
   220 Extend to get a chain map $f: F_*^\ep \to F_*^\ep$.
   226 If $y$ is a field defined on a neighborhood of *, define $s(y) = y$ if
   226 If $y$ is a field defined on a neighborhood of *, define $s(y) = y$ if
   227 * is a labeled point in $y$.
   227 * is a labeled point in $y$.
   228 Otherwise, define $s(y)$ to be the result of adding a label 1 (identity morphism) at *.
   228 Otherwise, define $s(y)$ to be the result of adding a label 1 (identity morphism) at *.
   229 Extending linearly, we get the desired map $s: J_* \to K_*(C)$.
   229 Extending linearly, we get the desired map $s: J_* \to K_*(C)$.
   230 It is easy to check that $s$ is a chain map and $s \circ i = \id$.
   230 It is easy to check that $s$ is a chain map and $s \circ i = \id$.
       
   231 What remains is to show that $i \circ s$ is homotopic to the identity.
   231 
   232 
   232 Let $N_\ep$ denote the ball of radius $\ep$ around *.
   233 Let $N_\ep$ denote the ball of radius $\ep$ around *.
   233 Let $L_*^\ep \sub J_*$ be the subcomplex 
   234 Let $L_*^\ep \sub J_*$ be the subcomplex 
   234 spanned by blob diagrams
   235 spanned by blob diagrams
   235 where there are no labeled points
   236 where there are no labeled points