The linear cosmological perturbation theory of an almost homogeneous and isotropic perfect fluid universe is reconsidered and formally simplified by introducing new covariant and gauge-invariant variables with physical interpretations on hypersurfaces of constant expansion, constant curvature or constant energy density. The existence of conserved perturbation quantities on scales larger than th...

Generation of linearly unstable streamers and nonlinearly saturated zonal flows have been investigated using two-dimensional simulations of interchange mode turbulence. It has been shown that nonlinear diamagnetic interactions tend to inhibit spectral cascades towards larger length scales and consequently suppress the nonlinear excitation of zonal flows. The latter has also been found to be in ...

The perturbative description of the Quark-Gluon Plasma (QGP) breaks down even at very high temperatures [1]. The reason for this is the generation of different length (time) scales at finite temperature. At high temperatures (T ≫ ΛQCD) the gauge coupling constant is small g ≪ 1 and well separated length scales exist: 1/T ≪ 1/(gT ) ≪ 1/(gT ). For such high temperatures the region of applicabilit...