247 citations · 2k across the 37 of their papers we have counts for
15 papers · 1 filter
Implications of Gravitational-wave Production from Dark Photon Resonance to Pulsar-timing Observations and Effective Number of Relativistic Species
Ryo Namba, Motoo Suzuki
The coherent oscillation of axionic fields naturally drives copious production of dark photon particles in the early universe, due to resonance and tachyonic enhancement. During th…
Mixed Non-Gaussianity from Axion-Gauge Field Dynamics
Tomohiro Fujita, Ryo Namba, Ippei Obata
We study scalar-tensor-tensor cross correlation generated by the dynamics of interacting axion and SU(2) gauge fields during inflation. We quantize the quadra…
Inflationary magneto-(non)genesis, increasing kinetic couplings, and the strong coupling problem
Hossein Bazrafshan Moghaddam, Evan McDonough, Ryo Namba +1
We study the generation of magnetic fields during inflation making use of a coupling of the inflaton and moduli fields to electromagnetism via the photon kinetic term, and assuming…
Does the detection of primordial gravitational waves exclude low energy inflation?
Tomohiro Fujita, Ryo Namba, Yuichiro Tada
We show that a detectable tensor-to-scalar ratio on the CMB scale can be generated even during extremely low energy inflation which saturates the BBN bound $ρ_{\rm…
Testing statistics of the CMB B-mode polarization toward unambiguously establishing quantum fluctuation of vacuum
Maresuke Shiraishi, Chiaki Hikage, Ryo Namba +2
The B-mode polarization in the cosmic microwave background (CMB) anisotropies at large angular scales provides a smoking-gun evidence for the primordial gravitational waves (GWs).…
Pre-reheating Magnetogenesis in the Kinetic Coupling Model
Tomohiro Fujita, Ryo Namba
Recent blazar observations provide growing evidence for the presence of magnetic fields in the extragalactic regions. While a natural speculation is to associate the production to…