176 citations · 521 across the 9 of their papers we have counts for
5 papers · 1 filter
Primordial Helium Abundance from CMB: a constraint from recent observations and a forecast
Kazuhide Ichikawa, Toyokazu Sekiguchi, Tomo Takahashi
We studied a constraint on the primordial helium abundance Y_p from current and future observations of CMB. Using the currently available data from WMAP, ACBAR, CBI and BOOMERANG,…
Neutrino mass constraint from CMB and its degeneracy with other cosmological parameters
Kazuhide Ichikawa
We show that the cosmic microwave background (CMB) data of WMAP can give subelectronvolt limit on the neutrino mass: m_nu < 0.63 eV (95% CL). We also investigate its degeneracy wit…
The Hubble constant and dark energy from cosmological distance measures
Kazuhide Ichikawa, Tomo Takahashi
We study how the determination of the Hubble constant from cosmological distance measures is affected by models of dark energy and vice versa. For this purpose, constraints on the…
Solving the cosmic lithium problems with primordial late-decaying particles
Daniel Cumberbatch, Kazuhide Ichikawa, Masahiro Kawasaki +3
We investigate the modifications to predictions for the abundances of light elements from standard Big-Bang nucleosynthesis when exotic late-decaying particles with lifetimes excee…
Cosmological Constraint on the Effective Number of Neutrino Species
Kazuhide Ichikawa
We discuss constraints on the effective number of neutrino species Nnu from recent cosmological observations such as CMB, LSS, BBN, including our own analysis which uses the WMAP a…