GALAXY FORMATION AND PHONONS

We investigate the possibility that the spectrum of pregalactic inhomogeneities results from quantum density fluctuations in the early Universe. A hydrodynamical description of matter is used, which is reasonable for galactic scales. The excitations of the physical degrees of freedom for longitudinal matter displacements, and the corresponding perturbations of the metric, called phonons for brevity, are shown to be treatable in terms of a scalar field. We derive the quadratic Lagrangian for this field directly from the Einstein-Fock action. Using the method of canonical quantization, we calculate the spectrum of inhomogeneities in the long-wave limit and find that its form is a model-independent power law, while its amplitude is defined by the evolution of the equation of state of the background matter. As an example we present a model in which the conditions needed for galaxy formation may be realized by the creation of phonons. ©Royal Astronomical Society Provided by the NASA Astrophysics Data System.