arXiv subjects

David Trotman

Publications and source records attributed to David Trotman.

7 recordsLinked to original sources

arXiv2017

On the local geometry of definably stratified sets

We prove that a theorem of Pawlucki, showing that Whitney regularity for a subanalytic set with a smooth singular locus of codimension one implies the set is a finite union of differentiable manifolds with boundary, applies to definable sets in polynomially bounded o-minimal structures. We give a refined version of Pawlucki's theorem for arbitrary o-minimal structures, replacing Whitney (b)-regularity by a quantified version, and we prove related results concerning normal cones and continuity of the density. We analyse two counterexamples to the extension of Pawlucki's theorem to definable sets in general o-minimal structures, and to several other statements valid for subanalytic sets. In particular we give the first example of a Whitney (b)-regular definably stratified set for which the density is not continuous along a stratum.

math.DG↗

arXiv2017

Whitney, Kuo-Verdier and Lipschitz stratifications for the surfaces y^a = t^b x^c +x^d

We specify the canonical stratifications satisfying respectively Whitney (a)-regularity, Whitney (b)-regularity, Kuo-Verdier (w)-regularity, and Mostowski (L)-regularity for the family of surfaces y^a = t^b x^c + x^d, where a, b, c, d are positive integers, in both the real and complex cases.

math.AG↗

arXiv2014

A geometric proof of the existence of definable Whitney stratifications

We give a geometric proof of existence of Whitney stratifications of definable sets in o-minimal structures.

math.DG↗

arXiv2013

Detecting Thom faults in stratified mappings

We state and prove several characterizations of Thom's regularity condition for stratified maps. In particular we extend to stratified maps some characterizations of Whitney (a) regularity, due to the second author.

math.AG↗

arXiv2012

Briançon-Speder examples and the failure of weak Whitney regularity

It is easy to find real algebraic varieties with weakly Whitney regular stratifications which are not Whitney regular, and we give such an example in section 3 below. No examples are known among complex analytic varieties however, so that the natural question arises : do Whitney regularity and weak Whitney regularity coincide in the complex case ? As a test, in this paper we study the well-known Briançon-Speder examples. We investigate systematically all of the (infinitely many) Briançon-Speder examples, and establish in particular that none of these examples are weakly Whitney regular. We determine all the complex curves along which Whitney regularity fails and all the complex curves along which weak Whitney regularity fails. It turns out that for each example there are a finite number of curves $γ_i$ such that weak Whitney regularity fails precisely along those curves tangent to one of the $γ_i$ at the origin.

math.AG↗

arXiv2012

On the multiplicities of families of complex hypersurface-germs

We show that the possible drop in multiplicity in an analytic family $F(z,t)$ of complex analytic hypersurface singularities with constant Milnor number is controlled by the powers of $t$. We prove equimultiplicity of $μ$-constant families of the form $f + tg + t^2h$ if the singular set of the tangent cone of $\{f = 0}$ is not contained in the tangent cone of $\{h = 0}$.

math.AG↗

arXiv2005

Equisingularity of sections, $(t^r)$ condition, and the integral closure of modules

This paper uses the theory of integral closure of modules to study the sections of both real and complex analytic spaces. The stratification conditions used are the (t^) conditions introduced by Thom and Trotman. Our results include a new simple proof showing how the (t^r) conditions improve under Grassman modification, and a characterization of the (t^r) conditions using the multiplicity of a submodule of the Jacobian module of the singularity. This gives numerical criteria for Verdier Equisingularity of families of sections of the space.

math.AG↗