I don't believe that gluons have been found to actually exist.

Sorry I couldn't resist

With the EM fields and gravity working against each other they have to reach a balancing point. This is Influenced directly by the Tempuratue and Mass.
Depending on where this balance lands we will see different amounts and types of energy discharge and results. Until an object hits the Black Hole stage it is always bleeding energy of some type and will break down to a new form, or Explode and Discharge all of the remaining energy.
When we do more research I am sure we will find new forms and Frequencies of energy, matter, space, and time but it will take new technology and open minds.
You apply this to the formation of stars of all types and extend it over the billions of years that it is taking place and all of it can be understood in a sense. Don't approach any of these subjects with a mind closed to your collegues and their ideas. If you do you block progress.

Thus, after having read the article, I don't see any information on how a quark's color charge is "screened" at high densities. Is this inferred from the article? Does the quark-gluon plasma, where individual quarks supposedly exist without pairs, necessarily mean that the strong force is not operative or irrelevant?

I think to claim a macro object made of this speculative stuff is even more speculative.

Also, there was no predictive power applied in the development of the quark star idea, the hallmark of a sound theory. Someone saw a thing that the standard neutron star theory could not account for, and made a speculative leap. This idea seems to be an attempt to bypass the difficulties of the neutron star idea vs. the actuality of observations that don't make sense in the context of the theory.

The above link goes to one of the most recent papers on this.

Snowflake

Now it is time to make observations before we assume we know what the truth is. A good first step would be to make black holes in a particle collider. That could really help us out here.

I strongly disagree with you Chris, in regards to science Wikipedia proved rather trustworthy. Since the topic of QCD is highly complicated only experts would want to contribute to it. Also, when your field of expertise is particle physics, one day you will want to confirm whether Wikipedia got the things your profession is all about right.

Wikipedia, just like science, is self-correcting. The more expert viewer an article has, the more it will evolve. The problem of vandalism is often exaggerated, especially when the topic is something as ideologically neutral as Quantum Chromodynamics. Who'd want to meddle with that?

On Wikipedia: I don't have a problem with someone quoting Dr. Seuss as long as it is relevant and they give credit where it is due. The risk is always that other readers will judge a person/research by its weakest reference.

AJames: It would depend. How many quarks on average are being held within each neutron? Original temperature and pressure play a role as well. I don't think we'll be able to come up with a constant ratio.

Strange or quark stars are held together by the colour-force NOT gravity. What gravity does is overcome their mutual repulsion and reduces the baryons into free quarks. But, theoretically, a chunk of "quarkonium" can have zero net colour charge and be stable, even down to quite small masses.

Neutronium – the free neutron "sea" of a neutron star – isn't stable and would explode violently from neutron decay without the neutron star's gravity to hold it together.

The data on the physical characteristics of nuclear matter has huge error-bars so the observations of neutron stars and similar compact objects is providing us with real data on how nuclear matter behaves under extreme conditions.

Furthermore, again the question of preservation of angular momentum is neglected here. I thought all neutron stars were flat rapidly rotating disks and were not round at all?

I also agree with the proposal that "coloured" quarks are theoretical particles used to explain the differences in neutron and protons, and they explain the strong force binding atoms together. Surely the best way to image quark (dwarf) stars as free "quark soup" – where quarks become free as electrons do in the Fermi Sea within stars.

# Chris Says:
June 30th, 2008 at 9:05 pm

Indeed Chris, I could have sourced all of the original material, but I couldn't be assed. The Wikipedia description is succinct, and, in my opinion, worth contributing in response to Bill's statement – "There has never been a quark detected in isolation; their existence can only be theorized and, in experiments, inferred. Is there a particle physicist who will step forward and say that quarks can form matter other than as constituents of other particles, like protons and electrons? I think not."

Well, apparently there is (not having a go at you Bill) – hence the Wikipedia reference. It goes without saying that information sourced on Wikipedia should be taken with a grain of salt – but this fact does not need to be stated every single time Wikipedia is referred to.

In reference to his other question, namely, can gravity alone hold such an object together – I'm not sure. Quarks carry the 'charges' of colour, mass, electric and weak isospin. If the colour force is shielded in a QGP, then that leaves three other forces. I would say seeing that gravity alone among these is universally attractive, and the density of an object such as a quark star is so high, then gravity would dwarf effects from the two intrinsically stronger electromagnetic and weak forces. But really, I'm just guessing.

Astrofiend's quote of Wikipedia was perfectly responsive: do physicists think there's a form of quark matter other than hadrons? Yes, and they call it QGP. It's more interesting in this context than the as-yet-unobserved single quarks because a neutron star's worth of quarks is going to be more than one.

"A thought on: "quarks held together by gravity". The electromagnetic "EM" force is ten to the 39th power stronger than the gravitational force. Quarks are held together more strongly than the strong nuclear force that binds nuclear particles, which in turn is stronger than the EM force. How then can this quoted statement possibly be true?"

In Quantum Chromodynamics, a process called quark deconfinement is supposed to take place, leading to what's called a quark-gluon plasma. Wikipedia says:

"A quark-gluon plasma (QGP) is a phase of quantum chromodynamics (QCD) which exists at extremely high temperature and/or density. This phase consists of (almost) free quarks and gluons, which are the basic building blocks of matter. Experiments at CERN's Super Proton Synchrotron (SPS) first tried to create the QGP in the 1980s and 1990s: the results led CERN to announce the discovery of a "new state of matter"[1] in 2000. Currently, experiments at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) are continuing this effort[2]. Three new experiments running on CERN's Large Hadron Collider (LHC), ALICE[3], ATLAS and CMS, will continue studying properties of QGP."

Apparently the colour-charge of the quarks is screened just as electric charge is screened in a 'normal' plasma. This is a bit beyond me, but there you go. I guess the only charge that the quarks effectively carry that is universally attractive is the 'charge' of mass, and so that is how you get the quarks held together by the gravitational force. This can all be found on wikipedia under "Quark-gluon plasma".

A thought on: "quarks held together by gravity". The electromagnetic "EM" force is ten to the 39th power stronger than the gravitational force. Quarks are held together more strongly than the strong nuclear force that binds nuclear particles, which in turn is stronger than the EM force. How then can this quoted statement possibly be true?