Padmanabhan, T.2012-03-022012-03-021991-09-03http://hdl.handle.net/11007/109The quantum theories of a scalar field interacting with external electromagnetic and gravitational fields respectively are compared. It is shown that several peculiar features, like the ambiguity of particle definition, thermal affects etc., which are thought to be special to quantum theory in curved spacetime, have analogues in the case of electromagnetism.enQuantum theoryQunatum gravityRindler framesHawking radiationPair creationExpanding universeArticle