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.
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
I have listed below, in reverse chronological order, recent and past events (conference presentations, etc), I have participated in.
Academic visits:
31st March - 14th April: Short-term visit to Prof. Shinji Mukohyama at Yukawa Institute for Theoretical Physics, Kyoto University, Japan.
10th April: One day visit to Prof. Teruaki suyama, Tokyo Institute of Technology, Tokyo, Japan
Conference presentations:
January 2, 2025; Chirality transfer in the photon-graviton conversion in early universe and production of high-frequency GWs, in parallel session in "33rd Indian Association for General Relativity and Gravitation (IAGRG)" at Birla Institute of Technology And Science (BITS) Pilani, Pilani Campus, India (January 02-04, 2025).
January 19, 2024; Maximal chirality transfer in the photon-graviton conversion in the early universe, Second Neighbourhood Cosmology Meeting on Dec 19 at Indian Institute of Science (IISc) Bangalore.
December 6, 2023; Oral presentation titled An effective field theory approach to understand the primordial magnetogenesis, in parallel session in “10th International Conference on Gravitation and Cosmology (ICGC)” at Indian Institute of Technology (IIT) Guwahati, India (December 6-9, 2023)
April 6, 2023; Seminar talk on "An effective field theory approach to understand the primordial magnetogenesis" at Yukawa Institute for Theoretical Physics, Kyoto University, Japan.
March 29, 2023; Talk on "Gertsenshtein-Zel’dovich effect: A plausible explanation for fast radio bursts?" at "International Conference on the Physics of the Two Infinities" at Kyoto University, Japan.
March 2023; Talk on "Gertsenshtein-Zel’dovich effect: A plausible explanation for fast radio bursts?" at "41st Annual Meeting of the Astronomical Society of India (ASI)" at IIT Indore.
Dec 19, 2022; Talk on "Gertsenshtein-Zel’dovich effect: A plausible explanation for fast radio bursts?" at 32nd meeting of Indian Association for General Relativity and Gravitation (IAGRG32), IISER Kolkata.
July 7, 2022; Talk on "A viable model to explain the Fast radio burst using the Gertsenshtein-Zel'dovich effect" at 23rd International Conference on General Relativity and Gravitation, China (GR-23). (Virtual)
July 5, 2022; Contributed talk on "Helical magnetic fields lead to baryogenesis" at Summer School on Cosmology 2022 at International Centre for Theoretical Physics (ICTP), Trieste, Italy.
March 25 - 29, 2022; Poster presentation in "40th Annual Meeting of the Astronomical Society of India (ASI)" at IIT Roorkee.
July 6, 2021; Talk on "Helical magnetic fields lead to baryogenesis" in Sixteenth Marcel Grossmann Meeting Conference (MG-16). (Virtual)
April 17, 2021; Invited talk on "Helical magnetic fields lead to baryogenesis" in the cosmology group at IIT Madras. (Virtual)
March 29 - April 2, 2021; Talk on "Helical magnetic fields from Riemann coupling" in Beyond Standard Model: From Theory to Experiment (BSM- 2021) organized by The Center for Fundamental Physics (CFP) at Zewail City of Science and Technology and Faculty of Engineering and Natural Sciences at Sabancı University. (Virtual)
Feb 18-23, 2021; Poster presentation in "39th Annual Meeting of the Astronomical Society of India (ASI)". (Virtual)
Dec 14-18, 2020; Talk on "Helical magnetic fields from Riemann coupling" in XXIV DAE-BRNS HIGH ENERGY PHYSICS SYMPOSIUM 2020, NISER, Odisha. (Virtual)
Oct 17-18, 2020; Talk on "Helical magnetic fields from Riemann coupling" in SYMPHY 2020 at Department of Physics, IIT Bombay. (Virtual)
June 22-26 2020; Poster presentation in CERN virtual workshop "Zooming in on Axions in the Early Universe". (Virtual)
Feb 13-17, 2020; Poster presentation in "38th Annual Meeting of the Astronomical Society of India (ASI)", at IISER Tirupati.
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.
