Magnetorotational instability in dense electron-positron-ion plasmas.

We in this manuscript analyzed the magnetorotational instability (MRI) by using a multi-component quantum fluid model with the effect of spin magnetization in a differentially rotating degenerate electron-positron-ion (e-p-i) quantum plasma. The electrons and positron having the same mass but opposite charge are taken to be degenerate whereas ions are considered as classical owing to their large inertia. The general dispersion relation is derived and a local dispersion relation for MRI is obtained by applying MHD approximations. To obtained MRI and to analyze the results numerically, reduced dispersion relation is derived using the local approximations. The obtained results are applied to the astrophysical situations exist there in the interiors of White Dwarfs and neutron stars. Contribution from spin magnetization and the number densities of electrons and positrons plays a vital role in the dynamics and can alter the instability. The increase in the electron number density, hence spin magnetization enhances the growth rate of the mode and leads the system to instability which results in the core collapse of certain massive stars.