Sam Wormley wrote in message
...
riskbert wrote:

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?

Fermions satisfy the Pauli exclusion principle - you can't put two
identical fermions in the same state. That's why we have chemistry: the
electrons stack up in "shells" at different energy levels, instead of
all going to the lowest-energy state, because they are fermions and
satisfy the exclusion principle.

http://hyperphysics.phy-astr.gsu.edu.../pauli.html#c2

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]