Detecting Primordial Black Holes with the Help of 21 cm Cosmology

Sajad Tabasi

Department of Physics, Sharif University of Technology

Supervisor: Shant Baghram

Abstract: The existence of primordial black holes has been proposed for about half a century, but so far we have not been able to have convincing observations to prove the existence of such black holes. With the discovery of gravitational waves, hopes for finding primordial black holes have increased again; So that in recent years, different ways have been proposed to reveal them. This matter becomes even more important when we know that these black holes can explain all or at least part of the missing matter of the universe known as dark matter. One of the proposed ways is to investigate the 21 cm line of hydrogen in the intergalactic medium. Over time, the temperature of the intergalactic medium is highly sensitive to the physical mechanisms within it. Thus, any physical phenomenon can increase or decrease the temperature. Since primordial black holes can accrete and pull in the surrounding gas and cause them to radiate, if they are abundant enough, they will have the ability to seriously affect the temperature of the intergalactic medium. In this thesis, we first plot the linear power spectrum by considering primordial black holes as dark matter and then show its effect on the temperature of the intergalactic medium. In addition, we calculate how much the temperature of the medium increases for different masses of these black holes and for what masses the whole dark matter can be considered as primordial black holes. Finally, we study a more realistic model and consider the nonlinear power spectrum, and in this regime, we measure the effect of primordial black holes on the power spectrum. The study of this regime is especially important because it can provide predictions for future observations of the 21 cm spectrum that can solve the problem of primordial black holes and dark matter.

چهارشنبه 16 شهریور 1401، ساعت 13:30

Wednesday 7 September 2022 – 13:30 Tehran Time

تالار پرتوی  – طبقه چهارم دانشکده فیزیک