riskbert wrote in message
om...
Why does Pauli's principle hold? Is it a mathematical principle or a
heuristic argument? And why does the principle break in sufficiently
dense objects which then collapse to form neutron stars?

Isolated white dwarf stars (degenerate electron gas) are not known
to collapse to neutron stars (degenerate neutron gas). High pressure
and temperature increase the rate and kinetic energy of collisions
between electrons and protons, thus enhancing the probability of
neutron formation (via the weak interaction) wherein lepton number
is conserved by neutrino emission. Furthermore, isolated neutron
stars are not known to collapse to black holes. It is known that
neutron star mass is inversely related to neutron star diameter.
[Old Man]