The Acoustic Wave Equation in the Expanding Universe: Sachs-Wolfe Theorem

Abstract

The acoustic field propagating in the early hot ($p=\epsilon/3$) universe ofarbitrary space curvature ($K=0, \pm 1$) is considered. The field equations arereduced to the d'Alembert equation in an auxiliary static Roberson-Walkerspace-time. Symbolic computation in {\em Mathematica} is applied.