The long-standing prediction of the Standard Model of elementary particles is that asymmetric neutrino environments cause rotation of linear polarization of electromagnetic wave—the birefringence. We demonstrate that this effect is strongly enhanced if additionally the photon is propagating through refractive medium, which effectively increases the photon exposure to the neutrino medium. Our estimate for an infrared laser beam in 1 m long optical fiber exposed to reactor antineutrino flux results in linear polarization rotation by the angle $\sim 4.6\times {10}^{-39}\mathrm{rad}$. We also derive the proper dependence of the effect on the angle between the directions of photon and neutrino propagation in the laboratory frame. For that purpose, we derive the correct form of the basis of polarization four-vectors, which differs from the one widely used in literature. We also estimate the subleading optical effect of the neutrino medium due to the neutrino dipole magnetic moment, in terms of a variation of the refractive index and its angular dependence. A rough monochromatic approximation points toward the existence of a resonant enhancement of the effect.

The extension of the Standard model by three right-handed neutrino fields exhibit appealing symmetry between left-handed and right-handed sectors, which is only violated by interactions. It can accommodate three flavor quasi-Dirac neutrino mixing scheme, which allows processes with violation of both lepton flavor and total lepton number symmetries. We propose a $6\times 6$ unitary matrix for parameterizing the mixing among three flavors of quasi-Dirac neutrino. This mixing matrix is constructed by two $3\times 3$ unitary matrices that diagonalizes the Dirac mass term in the Lagrangian. By only assuming the Standard Model $V-A$ weak interaction, it is found that probabilities of neutrino oscillations among active flavor states and effective masses measured by single beta decay, by neutrinoless double-beta decay and by cosmology only depend on single $3\times 3$ unitary matrix relevant to mixing of active neutrino flavors. Further, by considering $1\sigma$ and $3\sigma$ uncertainties in the measured oscillation probability of electron antineutrino from reactor, derivation of the constraint on the Majorana neutrino mass component is demonstrated. The consequence for effective Majorana neutrino mass governing the neutrinoless double-beta decay is discussed.

This is an erratum to the paper ‘Background for gravitational wave signal at LISA from refractive index of solar wind plasma’. In the original version of the manuscript Smetana ( 2020) an incorrect normalization of the resulting linear spectral densities |$\sqrt{S_{\mathrm{SW}}}$| has been applied. That lead to the overestimation roughly by factor of ∼1.5 of the LISA’s noise level caused by variations in the electron number density of the solar wind flowing through the LISA interferometric constellation.

In the context of top-quark condensation models, the top-quark alone is too light to saturate the correct value of the electroweak scale by its condensate. Within the seesaw scenario the neutrinos can have their Dirac masses large enough so that their condensates can provide significant contribution to the value of the electroweak scale. We address the question of a phenomenological feasibility of the top-quark and neutrino condensation conspiracy against the electroweak symmetry. Mandatory is to reproduce the masses of electroweak gauge bosons, the top-quark mass and the recently observed scalar mass of $125\,\mathrm{GeV}$ and to satisfy the upper limits on absolute value of active neutrino masses. To accomplish that we design a reasonably simplified effective model with two composite Higgs doublets. Additionally, we work with a general number $N$ of right-handed neutrino flavor triplets participating on the seesaw mechanism. There are no experimental constraints limiting this number. The upper limit is set by the model itself. Provided that the condensation scale is of order $10^{17-18}\,\mathrm{GeV}$ and the number of right-handed neutrinos is ${\cal O}(100-1000)$, the model predicts masses of additional Higgs bosons below $250\,\mathrm{GeV}$ and a suppression of the top-quark Yukawa coupling to the $125\,\mathrm{GeV}$ particle at the $\sim60\,%$ level of the Standard model value.

We study parity-violating birefringence induced by an asymmetric neutrino background in plasmas associated with active galactic nuclei (AGN). We derive a arising from the relative bulk motion between the neutrino medium and plasma, and show that it can produce an anomalous frequency dependence of the polarization-rotation angle, distinct from the ω − 2 scaling of Faraday rotation. This anomalous scaling can occur either at the resonance plasma frequency condition ω ≃ ω p , or when E ν 0 ≃ m ν ω / ω p lies within the range of the neutrino energy spectrum. We estimate the effect for three scenarios: jets propagating through the cosmic neutrino background ( C ν B ), jets with an internal flux of high-energy neutrinos, and accretion-disk plasma permeated by the C ν B . Of the three scenarios, the latter gives the largest rotation angle ϕ d ∼ 10 − 35 rad , at x-ray frequencies. Although the predicted rotation angles are below current polarimetric sensitivity, the identified spectral signatures provide a theoretical framework for probing neutrino asymmetries and AGN plasma properties independent of magnetic field models.