Small perturbations of the classical Heisenberg model
While there is a deep mathematical understanding of the 2D Ising model, its continuous $S^2$-valued counterpart—the classical Heisenberg model—remains one of the most significant challenges in mathematical physics. In 1975, Polyakov predicted that this system remains highly decorrelated at all positive temperatures due to its non-abelian symmetry. In this talk, I will discuss the behaviour of this model under small perturbations of the sphere's geometry. I will highlight how this problem naturally connects to questions in analysis, such as the properties of harmonic maps. No prior background in spin systems will be assumed. This is a joint work with Nathan de Montgolfier.

