Asymptotic cosmological solutions; orthogonal Bianchi type-I, III, IV, VII models

The authors investigate the evolution of spatially homogeneous cosmological models close to the initial singularity, in the distant future and at some intermediary stages. Their starting point for this investigation is the Einstein field equations with vacuum or perfect-fluid source, written as the reduced and regularised differential system given by Rosquist and Jantzen (1986). The possible asymptotic forms of the spacetime metric can be derived from approximate solution curves in the neighbourhoods of the singular points of this system.