arXiv subjects

Matías Menni

Publications and source records attributed to Matías Menni.

5 recordsLinked to original sources

arXiv2024

Bi-directional models of `radically synthetic' differential geometry

The radically synthetic foundation for smooth geometry formulated in [Law11] postulates a space T with the property that it has a unique point and, out of the monoid T^T of endomorphisms, it extracts a submonoid R which, in many cases, is the (commutative) multiplication of a rig structure. The rig R is said to be bi-directional if its subobject of invertible elements has two connected components. In this case, R may be equipped with a pre-order compatible with the rig structure. We adjust the construction of `well-adapted' models of Synthetic Differential Geometry in order to build the first pre-cohesive toposes with a bi-directional R. We also show that, in one of these pre-cohesive variants, the pre-order on R, derived radically synthetically from bi-directionality, coincides with that defined in the original model.

math.CT↗

arXiv2023

Separable MV-algebras and lattice-groups

General theory determines the notion of separable MV-algebra (equivalently, of separable unital lattice-ordered Abelian group). We establish the following structure theorem: An MV-algebra is separable if, and only if, it is a finite product of algebras of rational numbers, i.e., of subalgebras of the MV-algebra $[0,1]\cap\mathbb{Q}$. Beyond its intrinsic algebraic interest, this research is motivated by the long-term programme of developing the algebraic geometry of the opposite of the categroy of MV-algebras, in analogy with the classical case of commutative $K$-algebras over a field $K$.

math.RA↗

arXiv2022

Decidable objects and molecular toposes

We study several sufficient conditions for the molecularity/local-connectedness of geometric morphisms. In particuar, we show that if $\mathcal{S}$ is a Boolean topos then, for every hyperconnected essential geometric morphism ${p : \mathcal{E} \rightarrow \mathcal{S}}$ such that the leftmost adjoint $p_!$ preserves finite products, $p$ is molecular and ${p^* : \mathcal{S} \rightarrow \mathcal{E}}$ coincides with the full subcategory of decidable objects in $\mathcal{E}$. We also characterize the reflections between categories with finite limits that induce molecular maps between the respective presheaf toposes. As a corollary we establish the molecularity of certain geometric morphisms between Gaeta toposes.

math.CT↗

arXiv2019

The Unity and Identity of decidable objects and double-negation sheaves

Let ${\cal E}$ be a topos, ${{\rm Dec}({\cal E}) \rightarrow {\cal E}}$ be the full subcategory of decidable objects, and ${{\cal E}_{\neg\neg} \rightarrow {\cal E}}$ be the full subcategory of double-negation sheaves. We give sufficient conditions for the existence of a Unity and Identity ${{\cal E} \rightarrow {\cal S}}$ for the two subcategories of E above, making them Adjointly Opposite. Typical examples of such ${\cal E}$ include many `gros' toposes in Algebraic Geometry, simplicial sets and other toposes of `combinatorial' spaces in Algebraic Topology, and certain models of Synthetic Differential Geometry.

math.CT↗

arXiv2019

Level ε

Lawvere has observed that certain 'gros' toposes in algebraic geometry suggest the existence of an 'infinitesimal level', closely related to finite-dimensional local algebras. Motivated by this observation we propose an elementary definition of level ε associated to a local geometric morphism, establish some relevant basic properties suggested by geometric intuition, and give concrete descriptions of the level ε determined by several pre-cohesive geometric morphisms.

math.CT↗