[TorusAlgebra: some improvements, joint with Peter lipshitz@math.columbia.edu**20120102160654 Ignore-this: f9216182c14606df47a6cbe3e168a8ca ] hunk ./TorusAlgebra.tex 222 - procedure. The procedure produces a collection of tiles $T$, - arranged in a rooted tree which we call the {\em gluing tree}, and - which are glued along arcs (hence the - result is diffeomorphic to the standard disk). It also specifies a - assignment from arcs in the boundary instruction to tiles. - + procedure. The procedure produces: + \begin{itemize} + \item A collection of tiles $T$, arranged in a rooted tree which we + call the {\em gluing tree}. + \item A surface obtained by gluing tiles along arcs as specified by + the gluing tree. (This surface is homeomorphic to a disk.) + \item An assignment from arcs in the boundary instruction to tiles + in the gluing tree. + \end{itemize} hunk ./TorusAlgebra.tex 236 - arc $a_{i+1}$ in the boundary instruction. There are three cases. + arc $a_{i+1}$ in the boundary instruction. There are three cases. hunk ./TorusAlgebra.tex 249 - but $a_i$ {\em is} the fourth last arc on the boundary of $T$ encountered so far, then - $a_{i+1}$ is associated to the predecessor in the gluing tree of $T$. % - \smargin{RL: what does ``$a_{i+1}$ is associated to the predecessor - to $T$'' mean?}% - \smargin{Clearer now?} + but $a_i$ {\em is} the fourth arc on the boundary of $T$ encountered + so far, then + $a_{i+1}$ is associated to the predecessor in the gluing tree of + $T$. (This case does not involve any new gluing.) hunk ./TorusAlgebra.tex 256 - tile). + tile). (This case does not involve any new gluing.) hunk ./TorusAlgebra.tex 260 +\smargin{RL requests a figure, and a synopsis of which cases occur at + each step in the figure.} + hunk ./TorusAlgebra.tex 264 -which is tiled by copies of $T_0$, one of which is initial. % -\smargin{RL: I don't understand what the surface is in the - non-admissible case.}% -\smargin{PSO: let's discuss this} +which is tiled by copies of $T_0$, one of which is initial. hunk ./TorusAlgebra.tex 272 - admissible} - if, when we apply Construction~\ref{constr:BoundaryInstructions}, - the resulting tiles satisfy the following two properties: + admissible} if, when we apply + Construction~\ref{constr:BoundaryInstructions}, the resulting tiles + satisfy the following two properties: hunk ./TorusAlgebra.tex 276 - \item \label{req:FourArcsPerTile} For each tile $T$, there are four arcs assigned to $T$ - under the above construction; - \item \label{req:OrderOfArcs} The four arcs corresponding to any - given - tile $T$ appear in the - cyclic - order specified by $T_0$. + \item \label{req:FourArcsPerTile} For each tile $T$, there are four + arcs assigned to $T$ under the above construction; + \item \label{req:OrderOfArcs} The four arcs assigned to any given + tile $T$ appear in the cyclic order specified by $T_0$. hunk ./TorusAlgebra.tex 283 +\smargin{RL requests some examples of admissible versus non-admissible + boundary instructions} + hunk ./TorusAlgebra.tex 435 - Applying Construction~\ref{constr:BoundaryInstructions}, - to a left-extended sequence, we find that the first $i$ arcs, say, - are associated to tiles, and each of those tiles is assigned only - one arc. Thus, the sequence is clearly not admissible. Moreover, - if we factor $a_1\uplus\dots \uplus a_i$ of $r_1$, we obtain an - admissible sequence. Similarly, for a right-extended sequence, - if $a_m$ is the last arc in the initial tile, then the sequence is - right-extended by $a_{m+1}\uplus\dots\uplus a_n$. - \smargin{RL didn't follow this proof.} + Consider first a left-extended sequence, in which $r_1'$ is the + juxtaposition of $i$ arcs. Applying + Construction~\ref{constr:BoundaryInstructions}, the first $i$ arcs + are associated to different tiles, and each of those tiles is + assigned only one arc. Thus, the sequence is not strongly admissible + or right-extended admissible. Further, to obtain an admissible + sequence we must factor at least $i$ arcs from the beginning of + $r_1$. Moreover, if we factor more than $i$ arcs from the beginning + of $r_1$ then the tile corresponding to the last arc in $r_n$ will + be visited fewer than $4$ times. hunk ./TorusAlgebra.tex 484 -\smargin{RL: ``$1\leq i