Creation of scalar and dirac particles in asymptotically flat Robertson-Walker spacetimes

In the present article we obtain the exact solutions of the Klein-Gordon and Dirac equations for two models of Robertson-Walker spaces with asymptotically Minkowskian regions. Using the obtained exact solutions we calculate the density of scalar and Dirac particles created through Bogolubov transformations technique. For Dirac field it is shown that the creation rate of particles and anti particles are equal.