text/hochschild.tex
changeset 219 7e9a7b9605d3
parent 218 1acb5f508cf6
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   180 We show that $K_*(C)$ is quasi-isomorphic to $\bc_*(S^1)$.
   180 We show that $K_*(C)$ is quasi-isomorphic to $\bc_*(S^1)$.
   181 $K_*(C)$ differs from $\bc_*(S^1)$ only in that the base point *
   181 $K_*(C)$ differs from $\bc_*(S^1)$ only in that the base point *
   182 is always a labeled point in $K_*(C)$, while in $\bc_*(S^1)$ it may or may not be.
   182 is always a labeled point in $K_*(C)$, while in $\bc_*(S^1)$ it may or may not be.
   183 In particular, there is an inclusion map $i: K_*(C) \to \bc_*(S^1)$.
   183 In particular, there is an inclusion map $i: K_*(C) \to \bc_*(S^1)$.
   184 
   184 
   185 We define a left inverse $s: \bc_*(S^1) \to K_*(C)$ to the inclusion as follows.
   185 We want to define a homotopy inverse to the above inclusion, but before doing so
       
   186 we must replace $\bc_*(S^1)$ with a homotopy equivalent subcomplex.
       
   187 Let $J_* \sub \bc_*(S^1)$ be the subcomplex where * does not lie to the boundary
       
   188 of any blob.  Note that the image of $i$ is contained in $J_*$.
       
   189 Note also that in $\bc_*(S^1)$ (away from $J_*$) 
       
   190 a blob diagram could have multiple (nested) blobs whose
       
   191 boundaries contain *, on both the right and left of *.
       
   192 
       
   193 We claim that $J_*$ is homotopy equivalent to $\bc_*(S^1)$.
       
   194 Let $F_*^\ep \sub \bc_*(S^1)$ be the subcomplex where there there are no labeled
       
   195 points within distance $\ep$ of * on the right.
       
   196 (This includes * itself.)
       
   197 \nn{...}
       
   198 
       
   199 
       
   200 
       
   201 We want to define a homotopy inverse $s: \bc_*(S^1) \to K_*(C)$ to the inclusion.
   186 If $y$ is a field defined on a neighborhood of *, define $s(y) = y$ if
   202 If $y$ is a field defined on a neighborhood of *, define $s(y) = y$ if
   187 * is a labeled point in $y$.
   203 * is a labeled point in $y$.
   188 Otherwise, define $s(y)$ to be the result of adding a label 1 (identity morphism) at *.
   204 Otherwise, define $s(y)$ to be the result of adding a label 1 (identity morphism) at *.
   189 Extending linearly, we get the desired map $s: \bc_*(S^1) \to K_*(C)$.
   205 Extending linearly, we get the desired map $s: \bc_*(S^1) \to K_*(C)$.
   190 %Let $x \in \bc_*(S^1)$.
       
   191 %Let $s(x)$ be the result of replacing each field $y$ (containing *) mentioned in
       
   192 %$x$ with $s(y)$.
       
   193 It is easy to check that $s$ is a chain map and $s \circ i = \id$.
   206 It is easy to check that $s$ is a chain map and $s \circ i = \id$.
   194 
   207 
   195 Let $N_\ep$ denote the ball of radius $\ep$ around *.
   208 Let $N_\ep$ denote the ball of radius $\ep$ around *.
   196 Let $L_*^\ep \sub \bc_*(S^1)$ be the subcomplex 
   209 Let $L_*^\ep \sub \bc_*(S^1)$ be the subcomplex 
   197 spanned by blob diagrams
   210 spanned by blob diagrams