(adsbygoogle = window.adsbygoogle || []).push({}); Why "Tri-Bimaximal"?

[tex]\displaymath{U_{PMNS}=\begin{pmatrix}

\sqrt{2/3}& 1/\sqrt{3}& 0\\

-1/\sqrt{6}& 1/\sqrt{3}& 1/\sqrt{2}\\

1/\sqrt{6}& -1/\sqrt{3}& 1/\sqrt{2}\end{pmatrix}}[/tex]

This matrix implies [tex]\theta_{13}=0, \sin \theta_{12} = 1/\sqrt{3}[/tex] (ie. not maximal mixing) and [tex]\theta_{23}=\pi/4[/tex] (ie. maximal mixing)

OK, to my question, WHY do we call this matrix "Tri-Bimaximal"? How does this name come about? Two large mixing angles and the [tex]1/\sqrt{3}[/tex]?

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# Why Tri-Bimaximal ?

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