Abstract
We review the models unifying inflation and Primordial Black Hole (PBH) formation, which are based on the modified (Starobinsky-type) supergravity. We begin with the basic (Starobinsky) inflationary model of modified gravity and its alpha-attractor-type generalizations for PBH production, and recall how all those single-field models can be embedded into the minimal supergravity. Then, we focus on the effective two-field models arising from the modified (Starobinsky-type) supergravity and compare them to the single-field models under review. Those two-field models describe double inflation whose first stage is driven by Starobinsky’s scalaron and whose second stage is driven by another scalar belonging to the supergravity multiplet. The power spectra are numerically computed, and it is found that the ultra-slow-roll regime gives rise to the enhancement (peak) in the scalar power spectrum leading to an efficient PBH formation. The resulting PBH masses and their density fraction (as part of dark matter) are found to be in agreement with cosmological observations. The PBH-induced gravitational waves, if any, are shown to be detectable by the ground-based and space-based gravitational interferometers under construction.
Highlights
Accepted: 16 April 2021The oldest signal from the past to the present day is given by the Cosmic Microwave
The proposed extensions of the Starobinsky inflationary model in the modified supergravity can produce Primordial Black Hole (PBH) that could account for part of Cold Dark Matter
PBH generation can be efficiently catalyzed by primordial perturbations sourced by the Starobinsky scalaron coupled to another scalar of thegravitational origin
Summary
The oldest signal from the past to the present day is given by the Cosmic Microwave. Background (CMB) that emerged when electromagnetic radiation decoupled from matter and began propagating approximately 380,000 years after the Universe was born. We employ (a) the modified (Starobinsky) gravity and its supergravity extension, and combine it with (b) demanding Primordial Black Hole (PBH) formation after inflation and PBH as part of Dark Matter. There is no good reason for the absence of other fields during inflation It is our purpose in this paper to consider both types of the inflationary models and compare them.
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