The beginning of the universe is shrouded in mystery. The most common theory as to how the observable universe formed is explained by the Big Bang theory. This theory suggests how the universe expanded from an initial state of high density and temperature.
The focus of this study, conducted by Mr. H. V. Ragavendra, Dr. Pankaj Saha, and Prof. L. Sriramkumar, from the Department of Physics, IIT Madras, and Prof. Joseph Silk, from the Institut d’ Astrophysique de Paris, is on primordial black holes. Their aim is to identify what happened in the universe immediately after the big bang. Primordial black holes are hypothetical black holes that formed immediately after the big bang happened. A black hole is a region in the universe, where gravity is so strong that nothing, not even light can escape it.
Mr. H. V. Ragavendra 
Dr. Pankaj Saha 
Prof. L. Sriramkumar 
Prof. Joseph Silk
The researchers hope that by better understanding primordial black holes, it could be better understood as to what happened immediately after the big bang. They discovered that due to inflation in the universe, primordial black holes and secondary gravitational waves could have been formed. The theory of primordial black holes is closer to reality as gravitational waves can be detected by astronomical observatories around the world.
This study investigates whether black holes could have been formed in the early universe. Great density is required for black holes to be formed. Nowadays such high densities are found only in the stars. But high density alone is not enough for black holes to be formed. It depends on mass distribution as well. In this paper, the researchers hope to give a better understanding of primordial black holes. More research will be done into understanding what happened in the universe immediately after the big bang occurred.
Prof. Rajeev Kumar Jain, from the Department of Physics, Indian Institute of Science, Bangalore, gave the following observations on the paper: “Primordial black holes (PBH) are intriguing candidates for explaining the dark matter in the universe. Inflationary models producing PBHs also generate a secondary background of Gravitational Waves (GW), which can be detected with the future GW observatories. This paper explores a set of single-field inflationary models and examines the formation of PBHs as well as the secondary GWs in these models. While PBHs could contribute to the entire dark matter energy density in specific mass windows in these models, the associated GWs have a broad spectrum spanning a wide range in frequency, thereby presenting an exciting possibility of being simultaneously detected by multiple GW observatories. This paper further calculates the non-Gaussianities associated with the scalar perturbations and induced tensor perturbations, and finds them to be strongly scale-dependent in all the models. Small scale cosmological observations in future can potentially disentangle such models with the conventional slow-roll inflationary models.”
Article by Akshay Anantharaman
Here is the original link to the paper:
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.083510
