We study the closed universe recollapse conjecture for positively curved FRW models with a perfect fluid matter source and a scalar field which arises in the conformal frame of the R+ αR theory. By including ordinary matter, we extend the analysis of a previous work. We analyze the structure of the resulted fourdimensional dynamical system with the methods of the center manifold theory and the ...

We study the late time evolution of positively curved FRW models with a scalar field which arises in the conformal frame of the R + αR 2 theory. The resulted three-dimensional dynamical system has two equilibrium solutions corresponding to a de Sitter space and an ever expanding closed universe. We analyze the structure of the first equilibrium with the methods of the center manifold theory and...

We compare the observed Hubble diagram compiled from 280 supernovae redshift (RS) data in the range of z = 0.0141–8.1 with theoretical Hubble diagrams calculated on the basis of the Lambda cold dark matter (ΛCDM) model, the slowly expanding flat universe (SEU) model that expands according to equation (1) with ΩM = 1, and the static universe model. We show that the Hubble diagram clearly follows...

In this paper, we investigate cosmological particle production using quantum field theory (QFT). We will consider how production of scalar particles can occur in an expanding universe. By introducing a time-dependent energy parameter representing the time evolution of the universe, the initial vacuum state will be excited. Consequently, creation of particles is present. Here, our focus is mainl...