254 citations · 1.8k across the 51 of their papers we have counts for
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Cosmological abundance of the QCD axion coupled to hidden photons
Naoya Kitajima, Toyokazu Sekiguchi, Fuminobu Takahashi
We study the cosmological evolution of the QCD axion coupled to hidden photons. For a moderately strong coupling, the motion of the axion field leads to an explosive production of…
Refined Study of Isocurvature Fluctuations in the Curvaton Scenario
Naoya Kitajima, David Langlois, Tomo Takahashi +1
We revisit the generation of dark matter isocurvature perturbations in the curvaton model in greater detail, both analytically and numerically. As concrete examples, we investigate…
Cosmological stochastic Higgs stabilization
Jinn-Ouk Gong, Naoya Kitajima
We show that the stochastic evolution of an interacting system of the Higgs and a spectator scalar field naturally gives rise to an enhanced probability of settling down at the ele…
Small-scale structure and 21cm fluctuations by primordial black holes
Jinn-Ouk Gong, Naoya Kitajima
We discuss early structure formation of small scales sourced by primordial black holes (PBHs) which constitute a small part of present cold dark matter component. We calculate the…