Elementary particles and quantum geometry

Black holes are formed due to the gravitational collapse of matter - ordinary matter, consisting of the particles and excitations of the Standard Model that we know and love. These include electrons, photons, neutrinos, quarks, mesons etc, and their respective anti-particles. General Relativity tells us that the properties of (macroscopic) black holes are universal, in that they do not depend on the precise fraction of each particle species in the initial "mixture".

A black hole formed from the collapse of a non-rotating cloud of $ n$ electrons and $ n$ positrons will be neutral, non-rotating and of mass $ 2n m_e$, where $ m_e$ is the electron mass. Let us refer to this black hole as $ bh(n,e^-; n,e^+)$ or $ bh_e$ for short. A black hole formed from the collapse of cloud of $ m$ neutrinos and $ m$ anti-neutrinos, where $ m * m_{\nu} = n * m_e$ ($ m_{\nu}$ being the mass of a neutrino). According to our labeling scheme, this black hole will be labeled as $ bh(m,\nu;m,\bar\nu)$ or $ bh_{\nu}$ for short. Both black holes have the same mass $ M = n * m_e = m * m_{\mu} $ and thus the same horizon area $ A = GM/c^2$.