254 citations · 1.8k across the 51 of their papers we have counts for
8 papers · 1 filter
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…
Gravitational Waves from Domain Wall Collapse, and Application to Nanohertz Signals with QCD-coupled Axions
Naoya Kitajima, Junseok Lee, Kai Murai +2
We study for the first time the gravitational waves generated during the collapse of domain walls, incorporating the potential bias in the lattice simulations. The final stages of…
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…