Quantized fields and gravitational particle creation in f ( R ) expanding universes

摘要

The problem of cosmological particle creation for a spatially flat, homogeneous and isotropic universes is discussed in the context off(R)theories of gravity. Different from cosmological models based on general relativity theory, it is found that a conformal invariant metric does not forbid the creation of massless particles during the early stages (radiation era) of the universe.