Seesaw, coherence and neutrino oscillations

We present a prescription for consistently constructing non-Fock coherent flavour neutrino states within the framework of the seesaw mechanism, and establish that the physical vacuum of massive neutrinos is a condensate of Standard Model massless neutrino states. The coherent states, involving a finite number of massive states, are derived by constructing their creation operator. This construction fulfills automatically the key requirement of coherence for the oscillations of particles to occur. We comment on the inherent non-unitarity of the oscillation probability induced by the requirement of coherence.

Resonance refraction and neutrino oscillations

The refraction index and matter potential depend on neutrino energy and this dependence has a resonance character associated to the production of the mediator in the s−channel. For light mediators and light particles of medium (background) the resonance can be realized at energies accessible to laboratory experiments. We study properties of the energy dependence of the potential for different C-asymmetries of background. Interplay of the background potential and the vacuum term leads to (i) bump in the oscillation probability in the resonance region, (ii) dip related to the MSW resonance in the background, (iii) substantial deviation of the effective ∆m2 above the resonance from the low energy value, etc. We considered generation of mixing in the background. Interactions with background shifts the energy of usual MSW resonance and produces new MSW resonances. Searches of the background effects allow us to put bounds on new interactions of neutrinos and properties of the background. We show that explanation of the MiniBooNE excess, as the bump due to resonance refraction, is excluded.

Signatures of ultralight dark matter in neutrino oscillation experiments

We study how neutrino oscillations could probe the existence of ultralight bosonic dark matter. Three distinct signatures on neutrino oscillations are identified, depending on the mass of the dark matter and the specific experimental setup. These are time modulation signals, oscillation probability distortions due to fast modulations, and fast varying matter effects. We provide all the necessary information to perform a bottom-up, model-independent experimental analysis to probe such scenarios. Using the future DUNE experiment as an example, we estimate its sensitivity to ultralight scalar dark matter. Our results could be easily used by any other oscillation experiment.

Fluctuation Magnitude Calculation and Oscillation Probability Analysis of Tie-Line Active Power in Interconnected Power System

The historical data of wide area measurement system (WAMS) contains the daily record of the number of oscillations. The phenomenon, which the number of these oscillations suddenly increases at a certain frequency, indicates that the risk of weak damping oscillation with this frequency will increase. In other words, the statistical characteristics of these oscillations can reflect the system stability level. In this paper, the formulation of the small signal analysis including power disturbance on the power grid is given firstly. Then the relationship between the oscillation probability and damping ratio is obtained theoretically. Finally, a case study is carried out based on a 10-machine 39-bus power system. Simulation results verify the validity of the expression of oscillation amplitude of tie-line active power and the relationship between the oscillation probability and damping ratio. These theoretical results can be used to guide the power operator to assess the damping level of the power grid based on the daily number of oscillations recored by WAMS.