Consequences of Approximate $S_3$ Symmetry of the Neutrino Mass Matrix
Assuming that the neutrino mass matrix is dominated by a term with the permutation symmetry $S_{\scriptscriptstyle 3}$ it is possible to explain neutrino data only if the masses are quasi-degenerate. A sub-dominant term with an approximate $μ-τ$ symmetry leads to an approximate tri-bimaximal form. Experimental consequences are discussed.
hep-ph↗