BOSE-CONDENSATION AND SMALL-SCALE STRUCTURE GENERATION IN A RANDOM FORCE DRIVEN 2D-TURBULENCE

We consider two-dimensional flow stirred by a small-scale, white-in-ti me random noise in the zero viscosity limit. Numerical simulations sho w that, after a transient state, an inertial-range energy spectrum E(k ) is-proportional-to k(-x) with x = 5/3 +/- 0.05 is established by the inverse cascade process. This range grows in time until a Bose conden sate is formed at the largest scales in the system (k almost-equal-to 1). Prior to condensate formation the statistics of velocity differenc es are extremely close to Gaussian, and only after Bose condensation s trong deviations from Gaussian statistics are detected at small scales . The structures responsible for this effect are identified.