arXiv subjects
Publications and source records attributed to Gabriel Padilla.
In this article we give an equivariant version for the construction of generic models on presheaves of structures. We deal with first order structures endowed with a suitable action of some fixed group, say $G$; we call them $G$-structures. We show that every exact presheaf of $G$-structures $\mathcal{M}$ has a generic (equivariant) $G$-model $\mathcal{M}^{^{gen}}$.
We generalize the Generic Model Theorem for equivariant presheaves of structures; extending the results of Macintyre and Caicedo. We also introduce a new class of generic cohomologies and show how, for some examples, they simplify to non standard cohomologies. Key words and phrases: Generic Model Theorem, Equivariant Structures, Equivariant Cohomology. Primary fields: Model Theory. Equivariant sheaf cohomology.
In this paper we introduce a new topological Ramsey space whose elements are infinite ordered polyhedra. Then, we show as an application that the set of finite polyhedra satisfies two types of Ramsey property: one, when viewed as a category over $\mathbb N$; the other, when considered as a class of finite structures. The (ordered) random polyhedron is the Fraisse limit of the class of finite ordered polyhedra; we prove that its group of automorphisms is extremely amenable. Finally, we present a countably infinite family of topological Ramsey subspaces; each one determines a class of finite ordered structures which turns out to be a Ramsey class. One of these subspaces is Ellentuck's space; another one is associated to the class of finite ordered graphs whose Fraisse limit is the random graph. The Fraisse limits of these classes are not pairwise isomorphic as countable structures and none of them is isomorphic to the random polyhedron.
In this article we prove that stratified spaces and other geometric subfamilies satisfy categorical Fraïssé properties, a matter that might be of interest for both geometers and logicians. As a motivation we show a new example of a stratified pseudomanifold that satisfies the finite oscillation property with respect to a smooth stratified action. Part of this work was presented by the authors at the First Meeting of Logic and Geometry in Bogotá, on Sept. 2010.
In this article we study some interesting properties of the $q$-Analog singular homology, which is a generalization of the usual singular homology, suitably adapted to the context of $N$-complex and amplitude homology \cite{kapranov}. We calculate the $q$-Analog singular homology of a convex space. Although it is a local matter; this is an important step in order to understand the presheaf of $q$-chains and its algebraic properties. Our result is consistent with those of Dubois-Violètte & Henneaux \cite{dubois3}. Some of these results were presented for the XVIII Congreso Colombiano de Matemáticas in Bucaramanga, 2011.
A classical result says that a free action of the circle $\Bbb{S}^1$ on a topological space $X$ is geometrically classified by the orbit space $B$ and by a cohomological class ${H}^{^{2}}{(B,\Bbb{Z})}$, the Euler class. When the action is not free we have a difficult open question: $Π$ : "Is the space $X$ determined by the orbit space $B$ and the Euler class?" The main result of this work is a step towards the understanding of the above question in the category of unfolded pseudomanifolds. We prove that the orbit space $B$ and the Euler class determine: * the intersection cohomology of $X$, * the real homotopy type of $X$.
This article is devoted to the study of smooth desingularization, which are customary employed in the definition of De Rham Intersection Cohomology with differential forms. In this paper we work with the category of Thom-Mather simple spaces. We construct a functor which sends each Thom-Mather simple space into a smooth manifold called its primary unfolding. Hence we prove that the primary unfoldings are unique up Thom-Mather isomorphisms.