6 papers
Hubble-Scale Tachyonic Shocks from Low-Scale Inflation -- A New Gravitational-Wave Window on Inflation
Haruto Masubuchi, Yuma Narita, Wen Yin
Current bounds on the tensor-to-scalar ratio imply that the energy scale of inflation may lie below the grand-unified scale. In this paper, we show that in a broad class of single-…
Relativistic Axion with Nonrelativistic Momenta: A Robust Bound on Minimal ALP Dark Matter
Yuma Narita, Wen Yin
The axion-like particle (ALP), a pseudo Nambu-Goldstone boson that couples to two photons, has been studied extensively in recent years as a dark matter candidate. For initial fiel…
Superheavy dark matter from the natural inflation in light of the highest-energy astroparticle events
Kohta Murase, Yuma Narita, Wen Yin
Superheavy dark matter has been attractive as a candidate of particle dark matter. We propose a ``natural" particle model, in which the dark matter serves as the inflaton in natura…
Revisiting axion dark matter with nonlinear transitions
Max Miyazaki, Yuma Narita, Deheng Song +2
Recently, two of the present authors showed that even when the axion momentum is much smaller than its mass, the axion can still behave like radiation if its energy density greatly…
Explaining the KM3-230213A Detection without Gamma-Ray Emission: Cosmic-Ray Dark Radiation
Yuma Narita, Wen Yin
Recently, a high-energy neutrino event, designated KM3-230213A, was observed by the KM3NeT/ARCA detector in the Mediterranean Sea. This event is characterized by a reconstructed mu…
QCD Axion Dark Matter from level crossing with refined adiabatic condition
Kai Murai, Yuma Narita, Fuminobu Takahashi +1
We investigate the level-crossing phenomenon in two-axion systems, where the mass eigenvalues intersect as the mass of one axion increases with the cooling of the universe. This ph…