254 citations · 1.8k across the 51 of their papers we have counts for
15 papers · 1 filter
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…
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…
Clustering of Primordial Black Holes from QCD Axion Bubbles
Kentaro Kasai, Masahiro Kawasaki, Naoya Kitajima +3
We study the clustering of primordial black holes (PBHs) and axion miniclusters produced in the model proposed to explain the LIGO/Virgo events or the seeds of the supermassive bla…
Power spectrum of domain-wall network and its implications for isotropic and anisotropic cosmic birefringence
Naoya Kitajima, Fumiaki Kozai, Fuminobu Takahashi +1
Recently, based on a novel analysis of the Planck satellite data, a hint of a uniform rotation of the polarization of cosmic microwave background photons, called isotropic cosmic b…
New scenario of QCD axion clump formation I: Linear analysis
Naoya Kitajima, Kazuhiro Kogai, Yuko Urakawa
The QCD axion acquires the potential through the non-perturbative effect of the QCD matters around the QCD phase transition. During this period, the direct interaction between the…
Primordial black holes in peak theory with a non-Gaussian tail
Naoya Kitajima, Yuichiro Tada, Shuichiro Yokoyama +1
In this paper, we update the peak theory for the estimation of the primordial black hole (PBH) abundance, particularly by implementing the critical behavior in the estimation of th…