Cosmology Seminar

The next cosmology seminar takes place on Friday 30th of September, seminar room E349 at 2pm. Our guest speaker will be Nilanjandev Bhaumik from the Indian Institute of Science (Bangalore, India).

At 2pm, room E349, Nilanjan Bhaumik (IIS), will be talking about

Stochastic gravitational waves background to probe the reheating histories in the presence of primordial black holes

Primordial black hole (PBH) is one of the most promising cold dark matter candidates in recent years. The signature of PBHs in the stochastic gravitational-wave background (SGWB) is natural as PBH formation requires a significant amplification in inflationary scalar curvature perturbation, which sources the tensor perturbation in second order and amplifies the SGWB. We explore this possibility to probe different possible reheating histories. We find that any change in reheating histories can shift the PBH mass range and the peak frequency of SGWB. Still, only the matter-dominated reheating phase can lead to an additional resonant amplification in SGWB at a very high frequency. Isocurvature perturbation from PBH distributions contributes to the adiabatic perturbation. It also leads to detectable amplification in the induced GW background and can contribute to Baryogenesis for ultra-low mass PBHs, which can dominate the universe for a small duration. Combining these two effects can help us probe primordial black hole scenarios and details of reheating histories, leaving diverse implications for cosmology and particle physics.