Constraining Almost Degenerate Three-Flavor Neutrinos
  We discuss constraints on a scenario of almost degenerate three-flavor neutrinos imposed by the solar and the atmospheric neutrino anomalies, hot dark matter, and neutrinoless double $\beta$ decays. It is found that in the Majorana version of the model the region with relatively large $\theta_{13}$ is favored and a constraint on the CP violating phases is obtained. 
Hisakazu Minakata and Osamu Yasuda