Extending previous work on the formation and the evaporation of black holes in conformal gravity, in the present paper we study the gravitational collapse of a spherically symmetric and electrically...

We investigate for viable models of inflation that can successfully produce dark matter (DM) from inflaton decay process, satisfying all the constraints from Cosmic Microwave Background (CMB) and from some other observations. In particular, we analyze near-inflection-point small field inflationary scenario with non-thermal production of fermionic DM from the decaying inflaton field during the reheating era. To this end, we propose two different models of inflation with polynomial potential. The potential of Model I contains terms proportional to linear, quadratic, and quartic in inflaton; whereas in Model II, the potential contains only even power of inflaton and the highest term is sextic in inflaton. For both the models, we find out possible constraints on the model parameters which lead to proper inflationary parameters from CMB data with a very small tensor-to-scalar ratio, as expected from a small-field model. With the allowed parameter space from CMB, we then search for satisfactory relic abundance for DM, that can be produced from inflaton via reheating, to match with the present-day cold dark matter (CDM) relic density for the parameter spaces of the DM χ mass and Yukawa couplings in the range 10⁻⁹ ≳ y_χ ≳ 10⁻¹⁵ and 10³GeV ≲ m_χ ≲ 10⁹GeV. The DM relic is associated with the inflection-points in each model via maximum temperature reached in the early universe during its production. Finally, we find out allowed parameter space coming out of combined constraints from stability analysis for both SM Higgs and DM decays from inflaton as well as from BBN and Lyman-α bounds.

We study the production of a beyond the Standard Model (BSM) free-streaming relativistic particles which contribute to $N_{\mathrm{eff}}$ and investigate how much the predictions for the inflationary analysis change. We consider inflaton decay as the source of this dark radiation (DR) and use the cosmic microwave background (CMB) data from Planck-2018 to constrain the scenarios and identify the parameter space involving couplings and masses of the inflaton that will be within the reach of next-generation CMB experiments like spt-3g, CMB-S4, CMB-Bhārat, PICO, CMB-HD, etc. We find that if the BSM particle is produced only from the interaction with inflaton along with Standard Model (SM) relativistic particles, then its contribution to $N_{\mathrm{eff}}$ is a monotonically increasing function of the branching fraction, $B_X$ of the inflaton to the BSM particle $X$; Planck bound on $N_{\mathrm{eff}}$ rules out such $B_X\gtrsim 0.09$. Considering two different analyses of Planck+bicep data together with other cosmological observations, $N_{\mathrm{eff}}$ is treated as a free parameter, which relaxes the constraints on scalar spectral index ($n_s$) and tensor-to-scalar ratio ($r$). The first analysis leads to predictions on the inflationary models like hilltop inflation being consistent with the data. Second analysis rules out the possibility that BSM particle $X$ producing from the inflaton decay in Coleman-Weinberg inflation or Starobinsky inflation scenarios. To this end, we assume that SM Higgs is produced along with the BSM particle. We explore the possibilities that $X$ can be either a scalar or a fermion or a gauge boson and consider possible interactions with inflaton and find out the permissible range on the allowed parameter space Planck and those which will be within the reaches of future CMB observations.

The entropy production scenarios due to the electroweak phase transition (EWPT) in the framework of the minimal extension of standard model, namely the two Higgs doublet model (2HDM), are revisited. The possibility of first order phase transition is discussed. Intense parameter scanning was done with the help of BSMPT, a C++ package. We perform numerical calculations in order to calculate the entropy production with numerous benchmark points.