MINISUPERSPACEInquantum gravity, thephase spaceis infinite dimensional as we are dealing with a field theory. An approximation which is sometimes taken is to only consider the largest wavelength modes of the order of the size of the universe when studyingcosmological models. This is theminisuperspaceapproximation. The validity of this approximation holds as long as theadiabatic approximationholds.An example would be to only consider the scale factor and Hubble constant for aFriedman-Robertson-Walkermodel.