The moduli space of matroids

In the first part of the paper, we clarify the connections between several algebraic objects appearing in matroid theory: both partial fields and hyperfields are fuzzy rings, fuzzy rings are tracts, and these relations are compatible with the respective matroid theories. Moreover, fuzzy rings are ordered blueprints and lie in the intersection of tracts with ordered blueprints; we call the objects of this intersection pastures. In the second part, we construct moduli spaces for matroids over pastures. We show that, for any non-empty finite set $E$, the functor taking a pasture $F$ to the set of isomorphism classes of rank-$r$ $F$-matroids on $E$ is representable by an ordered blue scheme $Mat(r,E)$, the moduli space of rank-$r$ matroids on $E$. In the third part, we draw conclusions on matroid theory. A classical rank-$r$ matroid $M$ on $E$ corresponds to a $\mathbb{K}$-valued point of $Mat(r,E)$ where $\mathbb{K}$ is the Krasner hyperfield. Such a point defines a residue pasture $k_M$, which we call the universal pasture of $M$. We show that for every pasture $F$, morphisms $k_M\to F$ are canonically in bijection with $F$-matroid structures on $M$. An analogous weak universal pasture $k_M^w$ classifies weak $F$-matroid structures on $M$. The unit group of $k_M^w$ can be canonically identified with the Tutte group of $M$. We call the sub-pasture $k_M^f$ of $k_M^w$ generated by ``cross-ratios' the foundation of $M$,. It parametrizes rescaling classes of weak $F$-matroid structures on $M$, and its unit group is coincides with the inner Tutte group of $M$. We show that a matroid $M$ is regular if and only if its foundation is the regular partial field, and a non-regular matroid $M$ is binary if and only if its foundation is the field with two elements. This yields a new proof of the fact that a matroid is regular if and only if it is both binary and orientable.Comment: 83 page

On algebraic supergroups, coadjoint orbits and their deformations

In this paper we study algebraic supergroups and their coadjoint orbits as affine algebraic supervarieties. We find an algebraic deformation quantization of them that can be related to the fuzzy spaces of non commutative geometry.Comment: 37 pages, AMS-LaTe

Structured frames

Bibliography: pages 141-144.Ehresmann in 1959 first articulated the view that a complete lattice with an appropriate distributivity property deserved to be studied as a generalized topological space in its own right. He called the lattice a local lattice. Here is the distributivity property: x ∧ Vxα = V(x∧xα). A map of local lattices should preserve finite meets and arbitrary joins (and hence top and bottom elements). Dowker and Papert introduced the term frame for a local lattice and extended many results of topology to frame theory. At the 1981 international conference on categorical algebra and topology at Cape Town University a suggestion was made that a study of "uniform frames" (whatever they might be) would be an appropriate and useful start to a project concerned with examining, from a lattice theoretical point of view, the many topological structures which have gained acceptance in the topologist's arsenal of useful tools. It was felt that many of the pre-requisites for such a study had been established, and in fact one of the themes of the conference was the growing role of lattice theory in topology. The suggestion was eagerly accepted, and this thesis is the result

Quantale Modules, with Applications to Logic and Image Processing

We propose a categorical and algebraic study of quantale modules. The results and constructions presented are also applied to abstract algebraic logic and to image processing tasks.Comment: 150 pages, 17 figures, 3 tables, Doctoral dissertation, Univ Salern