My research focuses on a broad range of topics aimed at understanding the Physics of the Early Universe, with a particular focus on the following topics:
Inflation and Reheating
Cosmological perturbation theory
Primordial Gravitational waves
Primordial Black holes
Magnetic fields (astrophysical and cosmological)
By combining theoretical frameworks with observations, my goal is to uncover key insights into the fundamental physical processes operating in the early universe.
Mohammad Ali Gorji, Ashu Kushwaha, Teruaki Suyama; An upper limit on cosmological chiral gravitational wave background; e-print: 2601.13532
Ashu Kushwaha, Rajeev Kumar Jain; Probing Axion-Photon conversion via circular polarization imprints in the CMB V V-mode observations; e-print: 2510.22592
Ashu Kushwaha and Teruaki Suyama; Excursion Set Approach to Primordial Black Holes: Cloud-in-Cloud and Mass Function Revisited, e-print: 2509.25871
Ashu Kushwaha, Rajeev Kumar Jain; Constraining circular polarization of high-frequency gravitational waves with CMB, Phys. Rev. D 112, L021301 (2025) ; e-print: 2502.12517
Ashu Kushwaha, Rajeev Kumar Jain; Maximal chirality transfer in the photon-graviton conversion in the early universe, Phys. Rev. D 111, 023517 (2025) ; e-print: 2410.07338
Ashu Kushwaha and Teruaki Suyama; Constraining small-scale primordial magnetic fields from the abundance of primordial black holes, JCAP 12 (2024) 012 ; e-print: 2405.19693
Ashu Kushwaha, Sunil Malik, and S. Shankaranarayanan; Fast Radio Bursts signal high- frequency gravitational waves, International Journal of Modern Physics D; DOI: Received Honorable Mention in 2023 Essay Competition of the Gravity Research Foundation, USA; e-print: 2311.11150
Ashu Kushwaha, Abhishek Naskar, Debottam Nandi, and S. Shankaranarayanan ; Effective field theory of magnetogenesis identify necessary and sufficient conditions, JCAP 01 (2023) 045 ; e-print: 2207.05162
Ashu Kushwaha, Sunil Malik, and S. Shankaranarayanan ; Gertsenshtein-Zel'dovich effect: a plausible explanation for fast radio bursts?, Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 3, January 2024, Pages 4378–4387; e-print: 2202.00032
Ashu Kushwaha and S. Shankaranarayanan; Helical magnetic fields from Riemann coupling lead to baryogenesis, Phys. Rev. D 104, 063502 (2021); DOI: 10.1103/PhysRevD.104.063502, e-Print:2103.05339
Ashu Kushwaha and S. Shankaranarayanan; Helical magnetic fields from Riemann coupling, Phys. Rev. D 102, 103528 (2020) ; DOI: 10.1103/PhysRevD.102.103528 , e-Print: 2008.10825
Ashu Kushwaha and S. Shankaranarayanan; Galileon scalar electrodynamics, Phys. Rev. D 101, 065008 (2020); DOI: 10.1103/PhysRevD.101.065008 , e-Print: 1912.01393
Research Highlights
In this work, we studied the production of high-frequency chiral GWs from the conversion of the thermal photons in the early Universe.
In this work, we updated the constraints on small-scale magnetic fields in the radiation-dominated epoch by using the primordial black holes (PBHs) abundance.
The figure below shows some interesting astrophysical objects with magnetic fields and associated length scales.
About My PhD thesis
The origin of the cosmological magnetic field is an unresolved issue in modern cosmology. There is no compelling theoretical model to explain the presence of micro-Gauss strength magnetic fields in the galaxies and galaxy clusters. However, they could be of primordial origin and might have been generated due to cosmological processes during the early universe, specifically during inflation. In my PhD thesis, I studied constructing consistent field theoretical models to generate the primordial magnetic field with a primary focus on physics during the inflationary epoch. I have also studied the interesting consequences of small-scale magnetic fields (of compact objects).
Click here for my PhD thesis.
