We consider two scalar fields interacting through a χ * χφ * φ term in the presence of a Reissner-Nordstrøm black hole. Initially, only χ particles are present. We find that the produced φ particles are localized in a region around the black hole and have a tendency toward condensation provided that φ particles are much heavier than the χ particles. We also find that such a configuration is phenomenologically viable only if the scalars and the black hole have dark electric charges.

We introduce a toy model of scalar particles with a trilinear scalar coupling in cosmology. The trilinear coupling φ 2 χ causes production of non-relativistic φ particles through the process χχ → φφ where, initially, only relativistic χ particles are present. We consider the initial times of χχ → φφ and observe that the curved space effects promote formation of Bose-Einstein condensate of φ particles.

In this study, we give a thorough analysis of a general affine gravity with torsion. After a brief exposition of the affine gravities considered by Eddington and Schrödinger, we construct and analyze different affine gravities based on the determinants of the Ricci tensor, the torsion tensor, the Riemann tensor and their combinations. In each case we reduce equations of motion to their simplest forms and give a detailed analysis of their solutions. Our analyses lead to the construction of the affine connection in terms of the curvature and torsion tensors. Our solutions of the dynamical equations show that the curvature tensors at different points are correlated via non-local, exponential rescaling factors determined by the torsion tensor.

We introduce a method where particle physics processes in cosmology may be calculated by the usual perturbative flat space quantum field theory through an effective Minkowski space description at small time intervals provided that the running of the effective particle masses are sufficiently slow. We discuss the necessary conditions for the applicability of this method and illustrate the method through a simple example. This method has the advantage of avoiding the effects of gravitational particle creation in the calculation of rates and cross sections i.e. giving directly the rates and the cross sections due to the scatterings or the decay processes.