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Abstract
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The quantum magnetohydrodynamic model is employed in this paper to study the extraordinary
(XO) elliptically polarized electromagnetic wave dispersion in quantum plasmas with spin-1/2
magnetization and relativistic degeneracy effects, considering also the electron-exchange and
quantum diffraction of electrons. From the lower and upper calculated XO-modes, it is observed
that, for electrons on the surface of the Fermi-sphere, the lower XO-mode can excite the Cherenkov
radiation by crossing the Fermi-line, with some proper conditions depending on the values of
independent plasma parameters, such as the relativistic-degeneracy, the atomic-number of
constituent ions, and the magnetic field strength. Particularly, a lower electron number-density and
Cherenkov radiation frequency limits are found to exist, for instance, for given values of the plasma
ions atomic-number and the magnetic field strength below which the radiation can not be excited by
the electrons on the Fermi-surface. This lower density limit increases by decrease in the atomicnumber but decreases with decrease in the strength of the ambient magnetic field. It is remarkable
that in this research it is discovered that the maximal Cherenkov-radiation per unit-length (the
energy radiated by superluminal electrons traveling through the dielectric medium) coincides with
the plasma number-densities, which is present in compact stars with the maximal radiation
frequency lying in the gamma-ray spectrum. Current study can provide an important plasma
diagnostic tool for a wide plasma density range, be it the solid density, the warm dense matter, the
inertial confined or the astrophysical compact plasmas and may reveal an important cooling mechanism
for white dwarfs. Current findings may also answer the fundamental astrophysical question on the
mysterious origin of intense cosmic gamma-ray emissions.
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