Monte Carlo study of the XY-model on Sierpnski carpet

We have performed a Monte Carlo study of the classical XY-model on a Sierpi\' nski carpet, which is a planar fractal structure with infinite order of ramification and fractal dimension 1.8928. We employed the Wolff cluster algorithm in our simulations and our results, in particular those for the susceptibility and the helicity modulus, indicate the absence of finite-temperature Berezinskii-Kosterlitz-Thouless (BKT) transition in this system.