Th{\'e}orie de l'homotopie quantitative

Abstract

The aim of homotopy theory in topology is to simplify, after continuous deformation, continuous maps between topological spaces. What prevents this from happening are homotopy invariants. This raises quantitative questions: $\bullet$ Is the calculation of invariants possible (decidable)? If so, at what cost? $\bullet$ Is it possible to construct low-complexity representatives whose invariant values are prescribed? If so, at what cost? $\bullet$ How complex are the necessary deformations? The answers, often recent, are extremely varied. Moreover, many questions remain open, showing that topology has not said its last word, even in low dimensions.