The Spin-Density Threshold of an Einstein-Cartan Bounce: Critical Densities for Electron, Nucleon and Neutrino Fluids

For an electron fluid the threshold mass density is 1.598e+34 kg/m^3. For a neutron fluid it is 5.403e+40 kg/m^3, larger by a factor of 3.381e+06, which is the square of the neutron-to-electron mass ratio, as the analytic form requires. A neutrino fluid of particle mass 0.1 eV reaches threshold at only 6.118e+20 kg/m^3. Against the Planck density of 5.734e+79 kg/m^3, the neutron threshold sits at a fraction 9.422e-40 and the neutrino threshold at 1.067e-59. The radiation temperature equivalent of the neutron threshold is 1.592e+18 K. The alignment scan is the most consequential part of the table: reducing the aligned fraction of neutron spins to one part in a hundred raises the neutron threshold to 5.403e+44 kg/m^3, four orders of magnitude higher, because the spin term carries the square of the alignment. A completely unaligned fluid produces, in this averaged model, no threshold at any density. The study is a computation from stated assumptions, performed by the accompanying script; it is simulated, not measured.