scotth, its behavior as a “macro atom” is not exactly as you described it. Quantum effects are a direct function of size, not of “atomness”. It’s the small size of the atoms that allow them to behave “quantum mechanically”. As a coherent system, atoms aren’t nearly as “quantum mechanical” as say, an electron or a photon.
Your wranglings with temperature are illustrative of why its a difficult subject with which to deal. FWIW, there is no reason that neutrons can’t vibrate in thermal processes just like anything else. That’s thermodynamics. If they were at absolute zero, your system would have no entropy, which I would find even more implausible.
Basically, I take issue with your statement, “if it was possible to have a stable sample of pure neutronium”. Play along, if you will, and try to convince me of some way in which said “possibility” would occur so that a conclusion can be draw for how the object would look. I submit that you’re basically going to be effecting the substance so much that anything you do see will be more a function of making your “possibility” occur than the intrinsic properties of the stuff you’re trying to look at.
Whoever told you that light only interacts with charged particles is smoking something. Light interacts best with charged particles, but it can interact with neutral particles (i.e. photons) as well (this is just surpressed by some number of factors of [symbol]a[/symbol]). Also, since neutrons aren’t elementary particles and are actually composed of charged quarks, light can certainly interact with the individual quarks as well. I have no idea what neutronium looks like, but it’s certainly not transparent.
For the example of light interacting with light, look up “scattering of light by light,” which I believe is Delbruck scattering (which I almost undoubtedly spelled wrong).
Just to report back on my last post… Delbruck scattering is actually scattering of light by the Coulomb fields of nuclei. Scattering of light by light is predicted but according to my copy of Sakurai (Advanced QM, not Modern) was too small to detect as of the mid 60s, when the book was written. I have no idea if resolution has advanced enough so that this could be detected; he quotes a cross section of 4 x 10[sup]-31[/sup] cm[sup]2[/sup] at [symbol]w[/symbol] = m, where m is (I believe) the mass of the virtual particle that carries the interaction.
I’ve heard estimates that put as much as 10% of the mass of a neutron star in protons. It’s predominantly neutrons, but not exclusively.
As for temperature: Neutron stars do, in fact, have a temperature, which is how we can see them. A neutron star produces light in the same manner as any hot object (that is to say, above absolute zero) and cools down in the process. As long as it’s hotter than its surroundings, it’ll keep on emitting more energy than it absorbs, so a neutron star that’s been around for a while would be quite cool. Neutronium is a superfluid, which probably means that it’s also a superconductor of heat, so the internal temperature would be very consistent.
And gr8guy, I applaud your enthusiasm, but it hardly takes “smoking something” for a person to neglect fine structure corrections.
So, the ultimate conclusion is that, yes, degenerate matter will expand to a less-compact state if freed from intense gravitational confinement?
Question, then… what would be the cause of this? Would it be repulsion due to Pauli’s exclusion principle (quarks don’t like being near each other), normal atomic vibration (particles like to keep moving slightly), or what? Any cites would be welcome… I’ve scoured the Internet and only found a few.