Astrophysics Webinar

Abstract: Inflation provides a natural mechanism for generating primordial perturbations that explain the anisotropies in the cosmic microwave background (CMB) over large scales. It can also lead to interesting phenomena over small scales, such as, the production of primordial black holes (PBHs) and associated secondary gravitational waves (GWs). My research is focused on constraining the models of inflation over a wide range of scales using these observables. In this talk, I will initially discuss comparison of models of inflation having a kinetically dominated initial epoch against the CMB data [1]. I will then discuss the generation of PBHs and secondary GWs in certain classes of inflationary models [2]. I shall present the predictions from these models on observables, namely the fraction of PBHs constituting dark matter today and the spectrum of energy density of the associated secondary GWs. Lastly, I will discuss a method of accounting for the scalar bispectrum in the calculation of the spectral density of secondary GWs [3]. I shall illustrate this method using canonical models and contrast the results against an alternative scenario [4]. Finally, I shall conclude with a brief summary and outlook of these works.

References :
1. H. V. Ragavendra, D. Chowdhury and L. Sriramkumar, Suppression of scalar power on large scales and associated bispectra, arXiv:2003.01099 [astro-ph.CO]
2. H. V. Ragavendra, P. Saha, L. Sriramkumar and J. Silk, PBHs and secondary GWs from ultra slow roll and punctuated inflation, Phys. Rev. D 103, 083510 (2021) [arXiv:2008.12202 [astro-ph.CO]
3. H. V. Ragavendra, Accounting for scalar non-Gaussianity in secondary gravitational waves, Phys. Rev. D 105, 063533 (2022) [arXiv:2108.04193 [astro-ph.CO]
4. H. V. Ragavendra, L. Sriramkumar and J. Silk, Could PBHs and secondary GWs have originated from squeezed initial states?, JCAP 05, 010 (2021) [arXiv:2011.09938 [astro-ph.CO]