13th International Conference on the Exact Renormalization Group 2026 (ERG2026)

Derivative Expansion, Frustrated Antiferromagnets and $O(N)\times O(2)$ models

3 Sept 2026, 11:40

20m

Gallery Room 1 (Bramber House)

Talk Parallel Session

Speaker

Nicolás Wschebor (Instituto de Física de la Facultad de Ingeniería, Udelar (Uruguay))

Description

We will present the “Derivative Expansion” as applied to the study of scalar models with $O(N)\times O(2)$ symmetry. These models describe Stacked Triangular Antiferromagnets, which have been the subject of a long-standing controversy regarding the order of the phase transition for the experimentally studied cases $N=2$ and $N=3$ in $d=3$. A brief review will be given of previous studies of these systems and recent advances in the use of the Derivative Expansion. It will be explained how these advances allow for the establishment of a small parameter in the calculation of long-distance properties of a wide variety of critical models. It will be explained why this is of interest not only in applications to statistical physics but also in many problems in quantum field theory. In the case of $O(N)\times O(2)$ symmetry, it allows us to establish with unprecedented accuracy that the transition for $d=3$ is first-order for both $N=2$ and $N=3$.