Quantum cosmology of multifield scalar matter: Some exact solutions

We consider gravity interacting with matter scalar fields and quantized in the superspace approach in which the wave functional is described by the Wheeler–DeWitt equations. Assuming the dominance of the homogeneous and isotropic geometry, we investigate the leading contribution to the wave functional in the minisuperspace approximation with the Friedmann–Robertson–Walker metric and scalar fields depending on the time parameter. We construct a model of several scalar fields with exponential potentials and kinetic terms admitting a special mixing such that it is ultimately possible to separate the variables in the Wheeler–DeWitt equation and find its exact solution in terms of special functions. We study the semiclassical approximation in detail and choose boundary conditions that allow selecting the physical solution for classical cosmologies.