Categories and Structures for Computational Topology
Date: October 23, 2006 at 1pm
Speaker: Denis Blackmore
We first describe the category $\mathcal{CT}^{k}$, $1\leq
k\leq\omega$, whose objects $V$ are locally compact subsets of a Euclidean
space possessing a finite, $C^{k}$ Whitney regular stratification
\[
V=M_{1}\cup M_{2}\cup\cdot\cdot\cdot\cup M_{s},
\]
with morphisms $\varphi:V\rightarrow W$ that are $C^{k}$ maps respecting the
stratifications of $V$ and $W$. It is shown that this category is especially
well suited to the formulation and solution of a wide range of problems in
computational topology involving geometric objects that are piecewise
differentiable manifolds or non-manifolds (varieties).
For one thing, the category $\mathcal{CT}^{k}$ can be seen to
include just about all of the geometric objects that one is likely to
encounter in computational toplogy applications. Moreover, this category
enjoys the property of having analogs of many of the most important and useful
structures and operations associated with differentiable manifolds. For
example, it is demonstrated that the objects in $\mathcal{CT}^{k}$ have
tubular-like neighborhoods, which can be used to reduce various shape
invariant analyses to local calculations (in these neighborhoods). More
particularly, they can be employed - as will be explained in a brief
description of current joint work with R. Kopperman and T. Peters - to
simplify certain questions pertaining to embedding equivalence or ambient
isotopy to questions of homeomorphism equivalence in tubular-like neighborhoods.