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Neutrino conversions in hot plasma

Kari Enqvist·Jukka Maalampi·V. B. Semikoz
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Abstract

We discuss the excitation of sterile neutrinos in the early universe using general quantum kinetic equations, which also incorporate a possible primordial magnetic field $B$. We find a new contribution to the excitation propability, which has its origin in the shrinkage of the spin vector. In the absence of $B$ nucleosynthesis implies the constraint $\mid Δm^2\mid\sin^22θ_0\lsim 1.6\times 10^{-6}~{\rm eV}^2$ which is more restrictive than previous estimates. We also present examples of possible stringent limits for $B\ne 0$.

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Kari Enqvist, Jukka Maalampi, V. B. Semikoz. 1995-05-02. Neutrino conversions in hot plasma. https://doi.org/10.1016/0550-3213(98)00480-5

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