XY Model — Vortex-Antivortex Dynamics & BKT Transition

H = -J Σ cos(θᵢ−θⱼ) | BKT: T_BKT = πJ/2 | Vortex: winding ±1 = ∮∇θ·dl / 2π
1.20
40
5
ON
Vortices: 0 | Antivortices: 0