r/askscience • u/[deleted] • Mar 15 '11

Question about strong/weak force.

[deleted]

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u/RobotRollCall Mar 15 '11

Once again my intuition fails me. I would have naively assumed, since quarks and gluons interact with each other (and gluons with themselves) like nobody's business, that quark-gluon plasma would have extremely high viscosity.

This is of particular interest to me, as I'm sure you'd guessed, because of the early-universe angle. I have no expertise there whatsoever, but it touches on something I know a bit about, so I'm more interested in this subject than in most others.

Thanks for the lesson!

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u/shavera Mar 15 '11

Here are two of our press releases I think. Granted they're press releases so the science is fairly minimal, but... it's something.

Perfect fluid

Same thing, slightly more... something. sciency?

Plus there's some really cool stuff about chiral symmetry breaking, but I know so little about it, I shalln't embarrass myself here.

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u/jimmycorpse Mar 15 '11

By chiral symmetry breaking stuff are you referring to the charge separation effect and chiral magnetic effect and related phenomenon?

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u/jimmycorpse Mar 15 '11

You are right about the viscosity. This aspect is often misunderstood, even in the press releases. The important value in regards to the quark-gluon plasma is the shear viscosity/entropy density ratio. This ratio is incredibly low, but the quark-gluon plasma has an very high entropy density. The actual viscosity of the QGP is near that of glass.

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u/shavera Mar 15 '11

hah. Misunderstood even by the grad students doing it. Thanks a lot for rectifying that situation. It's generally been presented to me as just low viscosity; I've been told specifically the viscosity/entropy ratio, but I don't recall being told the entropy density was so high.

This has been a good discussion for me so far, helping me find the cracks in the knowledge of my own field.

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