Quark-gluon plasma

  • #1
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Main Question or Discussion Point

Quark-gluon "plasma"

I understand that recently an estimated temperature of 5.5 trillion K was achieved at CERN. The phase state is described as a frictionless liquid. Is it still a plasma since the term continues to be used?

Also, up to what temperature is QCD considered valid?

http://blogs.nature.com/news/2012/08/hot-stuff-cern-physicists-create-record-breaking-subatomic-soup.html

EDIT: It seems QCD breaks down at 2 trillion K. Are there any quantum theories that are valid for quark-gluon plasmas if in fact they are true plasmas?.
 
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Answers and Replies

  • #2
422
3


Yes, it's definitely a plasma.

QCD is valid at all temperatures, as far as I know. You can unify the strong interaction with the eletromagnetic and weak forces at high enough energies, but QCD should still be "valid"
 
  • #3
2,123
79


Yes, it's definitely a plasma.

QCD is valid at all temperatures, as far as I know. You can unify the strong interaction with the eletromagnetic and weak forces at high enough energies, but QCD should still be "valid"
OK. Thanks for the response. But I added an edit to my first post because of this:

http://physicsworld.com/cws/article/news/2011/jun/23/quarks-break-free-at-two-trillion-degrees

I guess Lattice QCD is still QCD.
 
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  • #4
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I understand that recently an estimated temperature of 5.5 trillion K was achieved at CERN. The phase state is described as a frictionless liquid.
It isn't really frictionless, I think. Close enough for jazz though
 
  • #5
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Yes.Lattice is a numerical algorithm of QCD.
 
  • #6
tom.stoer
Science Advisor
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I guess Lattice QCD is still QCD.
Lattice QCD is a rigorous reformulation of the QCD equations tuned for lattice calculations and Monte Carlo simulations. It is an approach that allowes us for non-perturbative calculations, i.e. investigation of regimes where bound states dominate and where the coupling is large.

From a QCD perspective QCD remains valid at all energies, but there are other forces which will become stronger at higher energies and which may be unified with QCD; but this is outside the QCD scope.
 
  • #7
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Lattice QCD is a rigorous reformulation of the QCD equations tuned for lattice calculations and Monte Carlo simulations. It is an approach that allowes us for non-perturbative calculations, i.e. investigation of regimes where bound states dominate and where the coupling is large.
I'm familiar with the Monte Carlo method. For example, in Monte Carlo integration one has an intractable integral: [itex] I = \int_a^{b} f(x) dx [/itex] which is approximated by:

[itex] \hat I = \frac{b-a}{n} \sum_{i=1}^{n} f(x_{i}) [/itex] where [itex] x_i [/itex] are independent observations from a uniform distribution on the interval (a,b).

I'll try to figure out exactly what a, b, and n are in this context on my own and leave the functions undefined. I'll come back if I get stuck. Thanks
 
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  • #8
tom.stoer
Science Advisor
5,766
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In lattice QCD the integral to be evaluated is a so-called path integral
 

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