Generation of primordial perturbations in the early universe

The role of adiabatic perturbations in the evolution of the universe is discussed, with note taken of the instability produced in a homogeneous gravitating fluid by small perturbations. A gauge-invariant theory of potential perturbations is developed for the origin of fluctuations on a scale of galaxies and clusters after the first second. The perturbations are described using a gauge-invariant linear combination of hydrodynamic and gravitational potentials of disturbances of the matter velocity and the metric. The initial fluctuation phases are assumed to have been random, i.e., quantum or thermal, and equipartitioned in a Higgs field distribution. The correlated phases of the fluctuations would result in a growth mode which would reach a decay mode and produce the large-scale metric disturbances.