Limit on the neutrino mass from the WMAP three-year data

We derive an upper limit on the neutrino mass from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data alone by employing a deterministic minimization method based on a grid search in multiparameter space. Assuming the flat ΛCDM model with power-law adiabatic perturbations, we find ∑_^m_ν<2.0 eV in agreement with the result of the WMAP team. This result, the limit being nearly the same as that from the WMAP first-year data, means that the fundamental limit on the neutrino mass obtainable from the cosmic microwave background alone is already nearly met, as anticipated from the previous analysis. We also clarify the role of the polarization data in deriving the limit on the neutrino mass.