On 2008-03-08, Crown-Horned Snorkack <chornedsnorkack@[EMAIL PROTECTED]
> wrote:
> I am not quite sure of that. I suspect that a stable neutron matter
> would have small, but nonzero, concentration of protons and electrons.
Yes, I solidly agree. If there were no electrons, there would be no
electron degeneracy pressure keeping the neutrons from decaying.
> If you have a small decrease of density, you will have a small
> decrease of electron chemical potential - and beta decay will then
> act to cause a small increase in proton concentration.
Yes, that is the phase transition I mentioned. There is a *lot* of
energy in the electron degeneracy pressure, which will maintain the
temperature as the density is slowly reduced.
Even if it were suddenly decreased, the decaying neutrons would add
free energy back into the matter, increasing the temperature again.
> Of course, this depends on the speed of density reduction, and
> density itself.
Oh, no question there. That's exactly what I was saying.
At one extreme the neutron matter explodes into a shower of free
neutrons that (by comparison) take forever to decay into a rarefied
hydrogen plasma.
At the other extreme the neutron matter gradually enriches in
electrons (and protons) as the density is lowered. The temperature
remains approximately constant during this phase transition, and
nuclear reactions are common.
> This means that as you decrease the density of neutron matter, which
> starts with low proton concentration, it goes on to be neutron rich
> and proton poor even when discrete nuclei condense out.
If it were not for a large range of nuclear reaction equilibria, that
would probably be true. Starting from a neutron-rich state, many of
these reactions will produce free neutrons or other nuclei that will
beta decay.
It will be much, much later before the temperature and density drop
low enough that reactions between nuclei become unimportant.
- Tim
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