Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutrino Mixing: $A_4$ Variations   In the context of the non-Abelian discrete symmetry $A_4$, the neutrino mass
matrix has been studied extensively. A brief update is presented to focus on
the conceptual shift from tribimaximal mixing ($\theta_{13} = 0$, $\theta_{23}
= \pi/4$, $\tan^2 \theta_{12} = 1/2$) to $\underline{\rm cobimaximal}$ mixing
($\theta_{13} \neq 0$, $\theta_{23} = \pi/4$, $\delta_{CP} = \pm \pi/2$) which
agrees well with present data. Three specific realistic examples are proposed,
two with three and the third with just two parameters.

25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con