# Weil Diffeology I: Classical Differential Geometry

## TL;DR

This paper develops a category-theoretic framework for classical differential geometry using the Weil topos and Dubuc functor, aiming to formalize tangent spaces and modules in an axiomatic setting.

## Contribution

It introduces a category-theoretical axiomatization of the Weil topos with the Dubuc functor for classical differential geometry.

## Key findings

- Axiomatization of the Weil topos with Dubuc functor
- Formalization of tangent spaces as modules over the canonical ring
- Proof of tangent space properties in the axiomatic framework

## Abstract

Topos theory is a category-theoretic axiomatization of set theory. Model categories are a category-theoretical framework for abstract homotopy theory. They are complete and cocomplete categories endowed with three classes of morphisms (called fibrations, cofibrations and equivalences) satisfying certain axioms. Functors from the category of Weil algebras to the category of sets are called Weil spaces by Wolfgang Bertram and form the Weil topos} after Eduardo J. Dubuc. The Weil topos is endowed intrinsically with the Dubuc functor, a functor from a larger category containing Weil algebras to the Weil topos standing for the incarnation of each algebraic entity of the category in the Weil topos. The Weil functor and the canonical ring object are to be defined in terms of the Dubuc functor. The principal object in this paper is to present a category-theoretical axiomatization of the Weil topos with the Dubuc functor intended to be an adequate framework for axiomatic classical differential geometry and hopefully comparable with model categories. We will give an appropriate formulation and a rather complete proof of a generalization of the familiar and desired fact that the tangent space of a microlinear Weil space is a module over the canonical ring object.