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Register a new userCosmological effects of neutrino mixing
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We report on the recent result that a contribution to the dark energy can be achieved by the vacuum condensate induced by neutrino mixing phenomenon.
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The today estimated value of dark energy can be achieved by the vacuum condensate induced by neutrino mixing phenomenon. Such a tiny value is recovered for a cut-off of the order of Planck scale and it is linked to the sub eV neutrino mass scale. Contributions to dark energy from auxiliary fields or mechanisms are not necessary in this approach.
Several cosmologically distant astrophysical sources may produce high-energy cosmic neutrinos (E geq 10^6 GeV) of all flavors above the atmospheric neutrino background. We study the effects of vacuum neutrino mixing in three flavor framework on this cosmic neutrino flux. We also consider the effects of possible mixing between the three active neutrinos and the (fourth) sterile neutrino with or without Big-Bang nucleosynthesis constraints and estimate the resulting final high-energy cosmic neutrino flux ratios on earth compatible with currently existing different neutrino oscillation hints in a model independent way. Further, we discuss the case where the intrinsic cosmic neutrino flux does not have the standard ratio.
Hydrogen oscillation into a dark-sector state $H$ has recently been proposed as a novel mechanism through which hydrogen can be cooled during the dark ages -- without direct couplings between the Standard Model and dark matter. In this work we demonstrate that the requisite mixing can appear naturally from a microphysical theory, and argue that the startling deviations from standard cosmology are nonetheless consistent with observations. A symmetric mirror model enforces the necessary degeneracy between $H$ and $H$, and an additional twisted $B+L$ symmetry dictates that $H$-$H$ mixing is the leading connection between the sectors. We write down a UV completion where $sim$ TeV-scale leptoquarks generate the partonic dimension-12 mixing operator, thus linking to the energy frontier. With half of all $H$ atoms oscillating into $H$, the composition of the universe is scandalously different during part of its history. We qualitatively discuss structure formation: both the modifications to it in the Standard Model sector and the possibility of it in the mirror sector, which has recently been proposed as a resolution to the puzzle of early supermassive black holes. While the egregious loss of SM baryons mostly self-erases during reionization, to our knowledge this is the first model that suggests there should be missing baryons in the late universe, and highly motivates a continued, robust observational program of high-precision searches for cosmic baryons.
We study corrections to tri-bimaximal (TBM) neutrino mixing from renormalization group (RG) running and from Planck scale effects. We show that while the RG effects are negligible in the standard model (SM), for quasi-degenerate neutrinos and large $tanbeta$ in the minimal supersymmetric standard model (MSSM) all three mixing angles may change significantly. In both these cases, the direction of the modification of $theta_{12}$ is fixed, while that of $theta_{23}$ is determined by the neutrino mass ordering. The Planck scale effects can also change $theta_{12}$ up to a few degrees in either direction for quasi-degenerate neutrinos. These effects may dominate over the RG effects in the SM, and in the MSSM with small $tan beta$. The usual constraints on neutrino masses, Majorana phases or $tan beta$ stemming from RG running arguments can then be relaxed. We quantify the extent of Planck effects on the mixing angles in terms of mismatch phases which break the symmetries leading to TBM. In particular, we show that when the mismatch phases vanish, the mixing angles are not affected in spite of the Planck scale contribution. Similar statements may be made for $mu$-$tau$ symmetric mass matrices.
We consider a situation where the leading-order neutrino mass matrix is derived by a theoretical ansatz and reproduces the experimental data well, but not completely. Then, the next stage is to try to fully reproduce the data by adding small perturbation terms. In this paper, we obtain the analytical method to diagonalize the perturbed mass matrix and find a consistency condition that parameters should satisfy not to change sintheta_{12} much. This condition could cause parameter tuning and plays a crucial role in relating the added perturbation terms with the prediction analytically, in particular, for the case of the partially quasi-degenerated neutrino masses (m_2 simeq m_1) where neutrinoless double beta decays would be observed in the phase-II experiments.
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