Datta, Dhurjati Prasad2015-01-132015-01-132015-01-13http://hdl.handle.net/11007/2799There different methods viz. i) a perturbative analysis of the schrodinger 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 semiclassical Einstein equations with backreaction. This constitutes an extension of our earlier discussion on the topic.enQuantum cosmologyArticle