Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Can Neutrinos be Degenerate in Mass?   We reconsider the possibility that the masses of the three light neutrinos of
the Standard Model might be almost degenerate and close to the present upper
limits from Tritium beta decay and cosmology. In such a scenario, the
cancellations required by the latest upper limit on neutrinoless double-beta
decay enforce near-maximal mixing that may be compatible only with the
vacuum-oscillation scenario for solar neutrinos. We argue that the mixing
angles yielded by degenerate neutrino mass-matrix textures are not in general
stable under small perturbations. We evaluate within the MSSM the
generation-dependent one-loop renormalization of neutrino mass-matrix textures
that yielded degenerate masses and large mixing at the tree level. We find that
m_{nu_e} > m_{nu_mu} > m_{nu_tau} after renormalization, excluding MSW effects
on solar neutrinos. We verify that bimaximal mixing is not stable, and show
that the renormalized masses and mixing angles are not compatible with all the
experimental constraints, even for tanbeta as low as unity. These results hold
whether the neutrino masses are generated by a see-saw mechanism with heavy
neutrinos weighing approx. 10^{13} GeV or by non-renormalizable interactions at
a scale approx. 10^5 GeV. We also comment on the corresponding renormalization
effects in the minimal Standard Model, in which m_{nu_e} < m_{nu_mu} <
m_{nu_tau}. Although a solar MSW effect is now possible, the perturbed neutrino
masses and mixings are still not compatible with atmospheric- and
solar-neutrino data.

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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg