Physics

Mathematics

Mechanics

Classical XY model

Statistical physics

Statistics

Phase transition

Magnet

Spectral density

Turbulence

Condensed matter physics

Flow (mathematics)

Quantum mechanics

Fractals

We give a review of the properties of low-temperature magnetic fluctuations in a finite-size 2D XY system. The behavior of such a simple model closely resembles that of several complex systems, notably the spectrum of power fluctuations in enclosed turbulent flow and interface width in surface growth problems. It suggests moreover new ideas in the study of aging phenomena in disordered systems.

CRITICAL FLUCTUATIONS IN 2D XY MAGNETS