Supercritically charged objects and electron-positron pair creation

We investigate the stability and e⁺e^- pair creation of supercritically charged superheavy nuclei, u d QM nuggets, strangelets, and strangeon nuggets based on the Thomas-Fermi approximation. The model parameters are fixed by reproducing masses and charge properties of these supercritically charged objects reported in earlier publications. It is found that u d QM nuggets, strangelets, and strangeon nuggets may be more stable than Fe 56 at the baryon number A ≳315 , 5 ×10⁴, and 1.2 ×10⁸, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number ∼965 , while u d QM nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than 39, 433, and 2.7 ×10⁵. The e⁺e^- pair creation will inevitably start for superheavy nuclei with charge numbers Z ≥177 , for u d QM nuggets with Z ≥163 , for strangelets with Z ≥192 , and for strangeon nuggets with Z ≥212 . A universal relation Q /R_e=(m_e-μ_¯e) /α is obtained at a given electron chemical potential μ_¯e, where Q is the total charge and R_e the radius of electron cloud. The maximum number of Q without causing e⁺e^- pair creation is then fixed by taking μ_¯e=-m_e. For supercritically charged objects with μ_¯e<-m_e, the decay rate for e⁺e^- pair production is estimated based on the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. It is found that most positrons are emitted at t ≲10^-15 s , while a long lasting positron emission can be observed for large objects with R ≳1000 fm . The emission of positrons and electron-positron annihilation from supercritically charged objects may be partially responsible for the short γ -ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in x-ray spectra from galaxies and galaxy clusters.