122 citations · 1k across the 49 of their papers we have counts for
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Peaky Production of Light Dark Photon Dark Matter
Yuichiro Nakai, Ryo Namba, Ippei Obata
We explore a mechanism to produce a light dark photon dark matter through a coupling between the dark photon field and a spectator scalar field which plays no role in the inflation…
Stochastic effects on observation of ultralight bosonic dark matter
Hiromasa Nakatsuka, Soichiro Morisaki, Tomohiro Fujita +4
Ultralight bosonic particles are fascinating candidates of dark matter (DM). It behaves as classical waves in our Galaxy due to its large number density. There have been various me…
Cosmic Birefringence from Monodromic Axion Dark Energy
Silvia Gasparotto, Ippei Obata
The recently reported non-zero isotropic birefringence angle in Planck 2018 polarization data provides a tantalizing hint for new physics of axions. In this paper, we explain this…
New constraints on axion-gauge field dynamics during inflation from and BICEP/Keck data sets
Paolo Campeti, Ogan Özsoy, Ippei Obata +1
We present new constraints on spectator axion- gauge field interactions during inflation using the latest (PR4) and BICEP/Keck 2018 data releases. This model c…
Inflation with two-form field: the production of primordial black holes and gravitational waves
Tomohiro Fujita, Hiromasa Nakatsuka, Ippei Obata +1
Antisymmetric tensor field (two-form field) is a ubiquitous component in string theory and generally couples to the scalar sector through its kinetic term. In this paper, we propos…