4 papers
Large lepton asymmetry from axion inflation and helium abundance hinted by ACT
Di Wu, Yifan Hu, Kohei Kamada
The generation of helical magnetic fields and the associated chiral asymmetry via the chiral anomaly is a generic feature in pseudoscalar inflation. In the presence of a Chern--Sim…
Magnetic Helicity, Magnetic Monopoles, and Higgs Winding
Hajime Fukuda, Yuta Hamada, Kohei Kamada +2
Changes in magnetic helicity are often discussed across a variety of fields, from condensed matter physics to early universe cosmology. It is frequently stated that the helicity ch…
Gravitational waves from metastable cosmic strings in the delayed scaling scenario
Yifan Hu, Kohei Kamada
Recent observations by pulsar timing arrays (PTAs) such as NANOGrav, EPTA, PPTA, and CPTA suggest the presence of nanohertz stochastic gravitational wave background (GWB). While su…
Revisiting constraints on primordial magnetic fields from spectral distortions of cosmic microwave background
Fumio Uchida, Kohei Kamada, Hiroyuki Tashiro
The magneto-hydrodynamic decay of primordial magnetic fields can distort the black-body spectrum of the cosmic microwave background (CMB) by draining magnetic energy into thermal p…