Electron Positron Capture Rates and Beta-Equilibrium Condition for Electron-Positron Plasma with Nucleons

The exact reaction rates of beta processes for all particles at arbitrary degeneracy are derived, and an analytic beta-equilibrium condition ${\mu }_n={\mu }_p+2{\mu }_e$ for the hot electron-positron plasma with nucleons is found, if the matter is transparent to neutrinos. This simple analytic formula is valid only if electrons are nondegenerate, which is generally satisfied in the hot electron-positron plasma. Therefore, it can be used to efficiently determine the steady state of the hot matter with positrons.