Abstract
We investigate warm inflationary scenario in which the accelerated expansion of the early Universe is driven by chameleon-like scalar fields. Due to the non-minimal coupling between the scalar field and the matter sector, the energy-momentum tensor of each fluid component is not conserved anymore, and the generalized balance equation is obtained. The new source term in the energy equation can be used to model warm inflation. On the other hand, if the coupling function varies slowly, the model reduces to the standard model used for the description of cold inflation. To test the validity of the warm chameleon inflation model, the results for warm inflationary scenarios are compared with the observational Planck2018 Cosmic Microwave Background data. In this regard, the perturbation parameters such as the amplitude of scalar perturbations, the scalar spectral index and the tensor-to-scalar ratio are derived at the horizon crossing in two approximations, corresponding to the weak and strong dissipative regimes. As a general result it turns out that the theoretical predictions of the chameleon warm inflationary scenario are consistent with the Planck 2018 observations.
Highlights
Four decades after the introduction of the inflation model, it can be considered as one of the cornerstones of modern cosmology [1–9]
We investigate warm inflationary scenario in which the accelerated expansion of the early Universe is driven by chameleon-like scalar fields
Since the scalar field interacts with the matter sector, in these models one has a generalized energy conservation law, where there is a source for the scalar field, depending on the scalar field – matter coupling function, and on the matter Lagrangian
Summary
Four decades after the introduction of the inflation model, it can be considered as one of the cornerstones of modern cosmology [1–9]. One of the important requirements of the inflationary scenarios is to establish a physically realistic relation between the end of the early accelerated, de Sitter type evolution, and the beginning of the radiation-dominated epoch, which corresponds to the SBB model Based on this requirement, one can consider two different types of inflation, namely the super-cold and the warm models of inflation [88–100]. A crucial advantage of this model of inflation is that it does not need any preheating and reheating mechanisms to realize the connection between the end of inflation and the beginning of the radiation era [88–92] To see how this can be achieved, let us go back to the aforementioned crucial problem of initial quantum fluctuations, related to the super-cold inflation.
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