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This theoretical study examines how primordial neutrinos with nonzero temperature and chemical potential can emit Cherenkov plasmons when interacting with a background plasma of charged leptons. The researchers calculated energy emission rates using quantum field theory and applied their findings to neutrino clusters that could have formed in the early universe through interactions with hypothetical light scalar bosons. They identified specific temperature ranges and conditions under which this plasmon emission mechanism could efficiently cool these primordial neutrino clusters.
Why it matters
Understanding neutrino cooling mechanisms in the early universe helps refine models of cosmic structure formation and the evolution of matter in the universe's first moments. The work also contributes to theories about dark matter and exotic particles that may have influenced early cosmological development.
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Abstract: We study the emission of Cherenkov plasmons by the gas of neutrinos with a nonzero temperature and a chemical potential. The background plasma, consisting of charged leptons, is taken to be nonrelativistic. The energy emission rate is obtained for longitudinal plasmons. To get the neutrino emissivity we average quantum field theory matrix element over the distribution functions of incoming and outgoing particles. Our results are applied for the description of the cooling down of a neutrino cluster formed in the early universe. Such clusters can exist owing to the neutrino interaction with a hypothetical light scalar boson. Using particular cluster parameters, we demonstrate that the considered cooling mechanism is efficient for some clusters. We find the temperature range where the proposed cooling channel is valid. Some useful calculations of the polarization tensor, as well as the plasmon form factors and their dispersion relations are also provided.