Is the fate of black dwarfs to become neutron stars without proton decay?

[Dremmer]

Will black dwarfs eventually quantum tunnel into neutron stars if proton decay doesn't occur?

 

[IsometricPion]

Will black dwarfs eventually quantum tunnel into neutron stars if proton decay doesn't occur?

I haven't done the math to be sure, but physical considerations alone seem to make it (practically) impossible. In order for a black dwarf to tunnel into a neutron star state much of the matter would have to tunnel into a much smaller volume. While quantum tunneling of macroscopic masses over macroscopic distances may be possible under the correct conditions, it is mind-boggingly unlikely for it to occur on such scales (think once in many googles of years or more). It is much more likely that a black dwarf would encounter another star/black hole first (and in the process probably cease to be a black dwarf).

If I remember correctly, just considering semi-classical gravity would predict protons to decay by tunneling into a microscopic black hole which would then evaporate. Though, I guess we won't have a really good idea whether or not that happens until evidence is found for a theory of quantum gravity (or a model of particle physics that predicts decay).

 

[Chronos]

Neutrons resulting from proton decay would promply decay. The gravity of a black dwarf is too low to stabilize them. Free neutrons decay in about 7 minutes. Neutron stars are stable only because of their immense gravity.

 

[Forestman]

I had a book a long time ago on the universe. Anyway this book stated that the matter in things such as black dwarfs would quantum tunnel and fuse into iron if protons did not decay. Iron being the most stable element.

 

[qraal]

I had a book a long time ago on the universe. Anyway this book stated that the matter in things such as black dwarfs would quantum tunnel and fuse into iron if protons did not decay. Iron being the most stable element.

The book was drawing on conclusions from a paper by Freeman Dyson called "Time Without End", which discussed the very long distant future of matter. The "cold fusion" tunneling time all the way to iron was some immense figure, a multi-exponential number.