What is a Q Ball? (Physics)

Stravo · Post by **Stravo** » 2008-01-14 07:37pm

I watched the movie "Sunshine" this weekend. A fine science fiction film from the same director that did 28 Days later and Trainspotting. Despite a lot of annoying plot contrivances its worth a look for some gorgeous visuals and a nice statement on reason v. religion (in other words religious faith=psycho crazy) as well as a very cool finale.

Anyway the whole premise of the film rests on a physics phenomenon called a "Q Ball" from that I gathered on Wiki is that it is a new fangled particle but not sure what it actually does (its theoretical but not actually proven).

The Q ball somehow is killing the sun and we have to restart it with a mega bomb. Not sure how a quantum particle can kill the sun and immediately smelled bad science behind the plot.

Anyone want to clear up what a Q Ball is for the physics challenged like myself (and I suspect the writer of the movie as well)?

Kuroneko · Post by **Kuroneko** » 2008-01-14 10:33pm

If I understand Kusenko correctly, a q-ball would be a particular bound configuration of supersymmetric partners--supersymmetric theories predict a partner particle for every 'normal' particle (e.g., quark->squark). Squarks, having no spin, do not obey the exclusion principle and so their bound states can become rather large. Kusenko also claims that quarks scattering off a q-ball are reflected as antiquarks. The quality of this work I'm in no position to judge, but as an empirical matter, no supersymmetric partner particles have actually been observed.

Gullible Jones · Post by **Gullible Jones** » 2008-01-14 10:47pm

What? Quarks reflected as antiquarks? I assume it would affect the composition of the Q-ball as well, lest charge conservation be violated?

Kuroneko · Post by **Kuroneko** » 2008-01-14 10:58pm

Gullible Jones wrote:What? Quarks reflected as antiquarks? I assume it would affect the composition of the Q-ball as well, lest charge conservation be violated?

Yes, conservation of baryon number means that the baryon number of the q-ball must be increased by 2/3.

The Grim Squeaker · Post by **The Grim Squeaker** » 2008-01-15 12:34am

Kuroneko wrote:
Gullible Jones wrote:What? Quarks reflected as antiquarks? I assume it would affect the composition of the Q-ball as well, lest charge conservation be violated?
Yes, conservation of baryon number means that the baryon number of the q-ball must be increased by 2/3.

Sorry for the foolish question, but why would the conservation of the baryon number mean a 2/3 increase, unless the number is proportional or the proportion changes

Kuroneko · Post by **Kuroneko** » 2008-01-15 12:41am

DEATH wrote:Sorry for the foolish question, but why would the conservation of the baryon number mean a 2/3 increase, unless the number is proportional or the proportion changes :?:

Every quark has a baryon number of 1/3, and every antiquark has a baryon number of -1/3 by definition (that is because baryons are particles composed of three quarks). If a quark simply turns into an antiquark, that's a net change of -2/3 to the baryon number (one less quark: -1/3, one more antiquark: -1/3 again). This means the q-ball's baryon number should be increased by 2/3 to make the total baryon number come out to be the same as it was.

The Grim Squeaker · Post by **The Grim Squeaker** » 2008-01-15 12:45am

Ah, perfectly reasonable. Thanks

. (Sorry for asking, it's just that I think that the explanations that spiral up into University level astrophysics or math should be explained when possible, even to us poor Luddites, fools, jappers and mocking-men

)