254 citations · 1.8k across the 51 of their papers we have counts for
52 papers
Axion Isocurvature Perturbations Survive the Scaling Evolution of Axion Domain Walls
Naoya Kitajima, Junseok Lee, Kai Murai +2
We revisit the evolution of axion domain walls seeded by inflationary fluctuations. In our previous work, we showed that such domain-wall networks retain superhorizon correlations…
A Bound on Light Dark Photon Dark Matter
Naoya Kitajima, Shota Nakagawa, Fuminobu Takahashi +1
We derive a bound on dark photon dark matter scenarios where the dark photon mass is generated through the Higgs mechanism, based on the requirement that symmetry breaking must occ…
Stability of domain walls with inflationary fluctuations under potential bias, and gravitational wave signatures
Naoya Kitajima, Junseok Lee, Fuminobu Takahashi +1
A recent study has shown that domain walls with inflationary initial fluctuations exhibit remarkable stability against population bias due to long-range correlations, challenging t…
Primordial Origin of Supermassive Black Holes from Axion Bubbles
Kentaro Kasai, Masahiro Kawasaki, Naoya Kitajima +3
We study a modification of the primordial black hole (PBH) formation model from axion bubbles. We assume that the Peccei-Quinn scalar rolls down in the radial direction from a larg…
Nanohertz gravitational waves from cosmic strings and dark photon dark matter
Naoya Kitajima, Kazunori Nakayama
The recent observations by pulsar timing array (PTA) experiments suggest the existence of stochastic gravitational wave background in the nano-Hz range. It can be a hint for the ne…
Stochastic gravitational wave background from early dark energy
Naoya Kitajima, Tomo Takahashi
We study the production of stochastic gravitational wave background from early dark energy (EDE) model. It is caused by resonant amplification of scalar field fluctuations, which e…