Neutronium

[Guest Lambus]

.

.

.

.

.

.

.

.

.

.

[CraigD]

Although it does come under various names (neutrium, polyneutron) the basic premise is the same - its not observed in nature.. why is this? I thought it would form a rather stable system, what does the proton do to make the system more stable?

As previous posts have noted, free neutrons aren’t very stable, with a mean lifetime of about 15 minutes. Why protons make them stable is, I think, very complicated, but to put it in very simple, hand-waving terms…

 

Protons (which each contain a U, U, and D quark) and neutrons (which each contain an U, D, and D quark) are dominated by the strong nuclear force, which is carried by a complex “swarm” of gluons that hold together both the quarks within the each proton and neutron, and the quarks in different protons and neutrons. It’s important to visualize that over 90% of the mass of protons and neutrons are comprised not of their 3 quarks, but their vast swarm of gluons. (not much hand-waving yet)

 

This complex swarm of gluons (with some photons and W and Z bosons thrown in) is subtly different for different numbers of protons and neutrons in a nucleus, accounting for why some nuclei are stable, others not, and why free neutrons are not. (plenty of hand-waving now)

 

Gravity is the wild-card of particle physics – all particles are subject to it, no well-accepted particle responsible for it. Thus very intense gravity fields may change the conditions under which quarks and gluons interact, possibly permitting the existence of such strange objects as a neutron star – which is theoretically mostly a huge nuclei consisting of only neutrons – or even stranger a quark star, which is theoretically mostly a huge, weird sub-atomic particle, something like a proton or neutron, but with 10[math]^{57}[/math] or more quarks rather than the usual 3. It’s theoretically possible that black holes do not, as General Relativity and classical gravity suggest, contain singularities, but some even stranger mix of quarks, gluons, and other particles found in less weird mixes in everyday matter. (All this is weird beyond hand-waving, but, I think, a not-inaccurate summary of the current consensus of particle physics.)

[Qfwfq]

Protons (which each contain a U, U, and D quark) and neutrons (which each contain an U, D, and D quark) are dominated by the strong nuclear force, which is carried by a complex “swarm” of gluons that hold together both the quarks within the each proton and neutron, and the quarks in different protons and neutrons. It’s important to visualize that over 90% of the mass of protons and neutrons are comprised not of their 3 quarks, but their vast swarm of gluons.

Actually, a hadron is a complex swarm of quarks, antiquarks and gluons, with the usually (and far more often) mentioned two or three for a given type of hadron being nothing but the net quark-antiquark balance.

 

There are of course weak interactions in there as well.

 

The residual strong nuclear force is mediated by virtual light meson pions, between protons and neutrons.

 

The strong nuclear force is mediated by gluons between quarks.

Now, that's more like it! If you read what you quoted as "ref. 1" you'll see it was saying some quite different things. ;)

[Jay-qu]

Thanks Craig, that helps a lot. A quark star is what I actually thought a neutron star might be.

 

Is there any models of the nucleus where it is look upon as a single particle? A complex mix of quarks [lots of hand waving :)] that always form in ratios that appear to give neutron/proton ratios?

[Qfwfq]

Is there any models of the nucleus where it is look upon as a single particle? A complex mix of quarks [lots of hand waving :)] that always form in ratios that appear to give neutron/proton ratios?

Many models have been considered and that is but one possibility, the phenomenology of the different models are worked out and matched against lab data. The picture is AFAIK somewhat intermediate between that one and one in which individual nucleons are interacting with each other.

 

It is somewhat like you put a certain number of water drops into a tube and they don't become a single continuum, but they don't quite remain separate drops either. As some of those wikis show, the nucleons are continually interacting in a way that amounts to exchanging hadrons, mostly of 2 quarks each i. e. mesons, which is analogous to the drops of water exchanging little blobs of their molecules, but without glomming together much.

[Guest Lambus]

.

.

.

.

.

.

.

.

.

.

[Guest Lambus]

.

.

.

.

.

.

.

.

.

.

[snoopy]

To Jay-qu

 

The way I was taught the magic numbers are

2,8,20,28,50,82,126

 

Largely comes from experiment in which a neutron is removed from the nucleus and in these configurations the amount of energy required to remove a neutron is above what you would expect implying some sort of closed shell structure.

 

At the 'magic numbers' the shell is considered to be closed above this, that is if you added a neutron the nucleus is bound less tightly together and its easier to remove a neutron.

 

I was also taught not to worry too much about what actually goes on inside an atom. :lol:

 

But as far as I know its to do with the binding energy.

 

Cheers

:cup:

[Jay-qu]

Thanks snoopy - I was just looking for a reason that these numbers cropped up, thats all

[Guest Lambus]

.

.

.

.

.

.

.

.

.

.