fluctuationdissipationteorin
Fluctuationdissipationteorin is the Swedish name for the fluctuation–dissipation theorem, a central result in statistical physics and linear response theory. It relates spontaneous fluctuations in an equilibrium system to the way that system dissipates energy when driven slightly out of equilibrium. In other words, spontaneous microscopic variability and macroscopic susceptibility to applied perturbations are two aspects of the same underlying dynamics.
Historically, the idea appears in work on electrical noise by Johnson and Nyquist and was formalized in
Practical applications span condensed matter physics, electrical engineering (Johnson–Nyquist noise), Brownian motion and diffusion (Einstein relation),