  Three different methods viz. i) a perturbative analysis of the Schr\"odinger
equation ii) abstract differential geometric method and iii) a semiclassical
reduction of the Wheeler-Dewitt equation, relating Pancharatnam phase to vacuum
instability are discussed. An improved semiclassical reduction is also shown to
yield the correct zeroth order semicalssical Einstein equations with
backreaction. This constitutes an extension of our earlier discussions on the
topic
