24 citations · 54 across the 16 of their papers we have counts for
18 papers
Initial clustering of primordial black holes: A general formulation for arbitrary local non-Gaussianity
Hirotaka Ishijima, Teruaki Suyama, Ashu Kushwaha
Initial spatial clustering of primordial black holes (PBHs) induced by local-type non-Gaussianity (LNG) can substantially modify cosmological constraints on PBH abundance. Several…
Gravitational Waves from Primordial Black Holes: Connecting Low-Frequency Scalar-Induced Signatures to High-Frequency Binary Mergers
Ashu Kushwaha
Formation of primordial black holes (PBHs) requires a significant enhancement of curvature perturbations. This enhancement generates a twofold gravitational wave (GW) signature: a…
Secondary Production of Photons from ALP Dark Matter interacting with a Cosmological Magnetic Field
Abdias Aires, Robert Brandenberger, Ashu Kushwaha
Under the assumption that dark matter is a coherently oscillating pseudoscalar field coupled to electromagnetism by the usual Chern-Simons term, we study the production of secondar…
Revisiting Constraints on Primordial Curvature Power Spectrum from PBH Abundances
Ashu Kushwaha, Teruaki Suyama
Primordial black holes (PBHs) can form in the early Universe, during radiation domination, from the collapse of large-amplitude density perturbations shortly after horizon re-entry…
ALP Dark Matter, Cosmological Magnetic Fields and the Direct Collapse Black Hole Formation Scenario
Ashu Kushwaha, Robert Brandenberger
Assuming that dark matter is an ultralight pseudoscalar particle which couples to electromagnetism like an axion (an ALP), we demonstrate that the coupling of the cosmological magn…
An upper limit on cosmological chiral gravitational wave background
Mohammad Ali Gorji, Ashu Kushwaha, Teruaki Suyama
Within the standard framework in which electroweak sphaleron processes relate lepton and baryon number, we derive an upper limit on the amplitude of a chiral gravitational wave bac…
Probing Axion-Photon conversion via circular polarization imprints in the CMB -mode observations
Ashu Kushwaha, Rajeev Kumar Jain
In the presence of a background magnetic field, axions or axion-like particles (ALPs) can be resonantly converted to photons when their mass is nearly equal to the effective photon…
Excursion Set Approach to Primordial Black Holes: Cloud-in-Cloud and Mass Function Revisited
Ashu Kushwaha, Teruaki Suyama
The abundance and mass function of primordial black holes (PBHs) are often estimated using the Press-Schechter (PS) formalism. In the case of halo formation, the PS formalism suffe…
Constraining circular polarization of high-frequency gravitational waves with CMB
Ashu Kushwaha, Rajeev Kumar Jain
Circular polarization in the cosmic microwave background (CMB) offers a promising probe of the parity-violating physics of the early universe. In this paper, we propose a novel met…
Maximal chirality transfer in the photon-graviton conversion in the early universe
Ashu Kushwaha, Rajeev Kumar Jain
While photons and gravitons do not interact significantly, photons can be converted to gravitons in a background magnetic field -- a phenomenon known as the Gertsenshtein effect. I…
Constraining small-scale primordial magnetic fields from the abundance of primordial black holes
Ashu Kushwaha, Teruaki Suyama
The presence of magnetic fields in the early universe affects the cosmological processes, leading to the distinct signature, which allows constraining their properties and the gene…
Generation and effects of primordial magnetic fields during inflation
Ashu Kushwaha
In this thesis, we aim to investigate the mechanisms underlying the genesis of magnetic fields in the Universe and explore their potential in addressing the matter-antimatter asymm…
Fast Radio Bursts signal high-frequency gravitational waves
Ashu Kushwaha, Sunil Malik, S. Shankaranarayanan
There is growing evidence for high-frequency gravitational waves (HFGWs) ranging from MHz to GHz. Several HFGW detectors have been operating for over a decade, and two GHz events h…
Effective field theory of magnetogenesis identify necessary and sufficient conditions
Ashu Kushwaha, Abhishek Naskar, Debottam Nandi +1
At astrophysical and cosmological scales, there is a detectable amount of magnetic field. There are several probable origins for this observed magnetic field, including the possibi…
Gertsenshtein-Zeldovich effect: A plausible explanation for fast radio bursts?
Ashu Kushwaha, Sunil Malik, S. Shankaranarayanan
We present a novel model that may provide an interpretation for a class of non-repeating FRBs -- short (), bright () bursts of MHz-GHz frequency radi…
Helical magnetic fields from Riemann coupling lead to baryogenesis
Ashu Kushwaha, S. Shankaranarayanan
The spectrum of energy density fluctuations, baryon asymmetry, and coherent large-scale magnetic fields are the three observables that provide crucial information on physics at ver…
Helical magnetic fields from Riemann coupling
Ashu Kushwaha, S. Shankaranarayanan
We study the inflationary generation of helical magnetic fields from the Riemann coupling with the electromagnetic field. Most models in the literature introduce non-minimal coupli…
Galileon scalar electrodynamics
Ashu Kushwaha, S. Shankaranarayanan
We construct a consistent model of Galileon scalar electrodynamics. The model satisfies three essential requirements: (1) The action contains higher-order derivative terms, and obe…