Particle Production in Gravitational Fields
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- Institutt for fysikk 
In this thesis, we discuss the phenomenon of particle production in gravitational fields. We present the general framework in flat Friedmann-Robertson-Walker spacetimes and apply it to an asymptotically static model in two dimensions. In such cases, the particle number can be obtained analytically in the asymptotic future. We discuss ways to give a physical meaning to the particle number in expanding universes and apply it to the same model. We find that in this case, the method of instantaneous vacuum provide meaningful results for the particle number as long as the particle production is not too big. Finally, a model for production of massless scalar particles during inflation is discussed. In this model, the dominant contribution to the energy density and particle number comes from long-wavelength fluctuations produced during inflation, rather than quantum fluctuations produced after inflation.