diff -r 16d7f0938baa -r 071ec509ec4a text/hochschild.tex --- a/text/hochschild.tex Sun Jun 07 00:51:00 2009 +0000 +++ b/text/hochschild.tex Sun Jun 07 18:40:39 2009 +0000 @@ -405,55 +405,52 @@ \bd(m\otimes a) & = & ma - am \\ \bd(m\otimes a \otimes b) & = & ma\otimes b - m\otimes ab + bm \otimes a . } -In degree 0, we send $m\in M$ to the 0-blob diagram in Figure xx0; the base point +In degree 0, we send $m\in M$ to the 0-blob diagram $\mathfig{0.05}{hochschild/0-chains}$; the base point in $S^1$ is labeled by $m$ and there are no other labeled points. In degree 1, we send $m\ot a$ to the sum of two 1-blob diagrams -as shown in Figure xx1. -In degree 2, we send $m\ot a \ot b$ to the sum of 22 (=4+4+4+4+3+3) 2-blob diagrams as shown in -Figure xx2. -In Figure xx2 the 1- and 2-blob diagrams are indicated only by their support. +as shown in Figure \ref{fig:hochschild-1-chains}. + +\begin{figure}[!ht] +\begin{equation*} +\mathfig{0.4}{hochschild/1-chains} +\end{equation*} +\begin{align*} +u_1 & = \mathfig{0.05}{hochschild/u_1-1} - \mathfig{0.05}{hochschild/u_1-2} & u_2 & = \mathfig{0.05}{hochschild/u_2-1} - \mathfig{0.05}{hochschild/u_2-2} +\end{align*} +\caption{The image of $m \tensor a$ in the blob complex.} +\label{fig:hochschild-1-chains} +\end{figure} + +In degree 2, we send $m\ot a \ot b$ to the sum of 24 (=6*4) 2-blob diagrams as shown in +Figure \ref{fig:hochschild-2-chains}. In Figure \ref{fig:hochschild-2-chains} the 1- and 2-blob diagrams are indicated only by their support. We leave it to the reader to determine the labels of the 1-blob diagrams. +\begin{figure}[!ht] +\begin{equation*} +\mathfig{0.6}{hochschild/2-chains-0} +\end{equation*} +\begin{equation*} +\mathfig{0.4}{hochschild/2-chains-1} \qquad \mathfig{0.4}{hochschild/2-chains-2} +\end{equation*} +\caption{The 0-, 1- and 2-chains in the image of $m \tensor a \tensor b$. Only the supports of the 1- and 2-blobs are shown.} +\label{fig:hochschild-2-chains} +\end{figure} Each 2-cell in the figure is labeled by a ball $V$ in $S^1$ which contains the support of all 1-blob diagrams in its boundary. Such a 2-cell corresponds to a sum of the 2-blob diagrams obtained by adding $V$ as an outer (non-twig) blob to each of the 1-blob diagrams in the boundary of the 2-cell. -Figure xx3 shows this explicitly for one of the 2-cells. +Figure \ref{fig:hochschild-example-2-cell} shows this explicitly for one of the 2-cells. Note that the (blob complex) boundary of this sum of 2-blob diagrams is precisely the sum of the 1-blob diagrams corresponding to the boundary of the 2-cell. (Compare with the proof of \ref{bcontract}.) - - -\medskip -\nn{old stuff; delete soon....} - -We can also describe explicitly a map from the standard Hochschild -complex to the blob complex on the circle. \nn{What properties does this -map have?} - -\begin{figure}% -$$\mathfig{0.6}{barycentric/barycentric}$$ -\caption{The Hochschild chain $a \tensor b \tensor c$ is sent to -the sum of six blob $2$-chains, corresponding to a barycentric subdivision of a $2$-simplex.} -\label{fig:Hochschild-example}% +\begin{figure}[!ht] +\begin{equation*} +A = \mathfig{0.1}{hochschild/v_1} + \mathfig{0.1}{hochschild/v_2} + \mathfig{0.1}{hochschild/v_3} + \mathfig{0.1}{hochschild/v_4} +\end{equation*} +\begin{align*} +v_1 & = \mathfig{0.05}{hochschild/v_1-1} - \mathfig{0.05}{hochschild/v_1-2} & v_2 & = \mathfig{0.05}{hochschild/v_2-1} - \mathfig{0.05}{hochschild/v_2-2} \\ +v_3 & = \mathfig{0.05}{hochschild/v_3-1} - \mathfig{0.05}{hochschild/v_3-2} & v_4 & = \mathfig{0.05}{hochschild/v_4-1} - \mathfig{0.05}{hochschild/v_4-2} +\end{align*} +\caption{One of the 2-cells from Figure \ref{fig:hochschild-2-chains}.} +\label{fig:hochschild-example-2-cell} \end{figure} - -As an example, Figure \ref{fig:Hochschild-example} shows the image of the Hochschild chain $a \tensor b \tensor c$. Only the $0$-cells are shown explicitly. -The edges marked $x, y$ and $z$ carry the $1$-chains -\begin{align*} -x & = \mathfig{0.1}{barycentric/ux} & u_x = \mathfig{0.1}{barycentric/ux_ca} - \mathfig{0.1}{barycentric/ux_c-a} \\ -y & = \mathfig{0.1}{barycentric/uy} & u_y = \mathfig{0.1}{barycentric/uy_cab} - \mathfig{0.1}{barycentric/uy_ca-b} \\ -z & = \mathfig{0.1}{barycentric/uz} & u_z = \mathfig{0.1}{barycentric/uz_c-a-b} - \mathfig{0.1}{barycentric/uz_cab} -\end{align*} -and the $2$-chain labelled $A$ is -\begin{equation*} -A = \mathfig{0.1}{barycentric/Ax}+\mathfig{0.1}{barycentric/Ay}. -\end{equation*} -Note that we then have -\begin{equation*} -\bdy A = x+y+z. -\end{equation*} - -In general, the Hochschild chain $\Tensor_{i=1}^n a_i$ is sent to the sum of $n!$ blob $(n-1)$-chains, indexed by permutations, -$$\phi\left(\Tensor_{i=1}^n a_i\right) = \sum_{\pi} \phi^\pi(a_1, \ldots, a_n)$$ -with ... (hmmm, problems making this precise; you need to decide where to put the labels, but then it's hard to make an honest chain map!)