  Joint analysis of the results of the Neutrino-4 experiment and the data of
the GALLEX, SAGE and BEST experiments confirms the parameters of neutrino
oscillations declared by the Neutrino-4 experiment $(\Delta m_{14}^2= 7.3
\text{eV}^2$ and $\sin^2 2\theta_{14} \approx 0.36)$ and increases the
confidence level to $5.8\sigma$. Such a sterile neutrino thermalizes in cosmic
plasma, contributes 5% to the energy density of the Universe, and can explain
15-20% of dark matter. It is discussed that the extension of the neutrino model
by introducing two more heavy sterile neutrinos in accordance with the number
of types of active neutrinos but with very small mixing angles to avoid
thermalization will make it possible to explain the large-scale structure of
the Universe and bring the contribution of sterile neutrinos to the dark matter
of the Universe to the level of 27%. Sterile neutrinos are essentially
right-handed neutrinos. The dynamic process of the dark matter generation,
consisting of three right-handed neutrinos, is presented. Expansion of the
Standard Model by introducing right-handed neutrinos seems possible. The scheme
of masses and the scheme of mixing flavors are considered.
