# Quark-gluon plasma

1. Sep 26, 2012

### SW VandeCarr

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/2012/0...ts-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?.

Last edited: Sep 26, 2012
2. Sep 26, 2012

### soothsayer

Re: Quark-gluon "plasma"

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. Sep 26, 2012

### SW VandeCarr

Re: Quark-gluon "plasma"

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.

Last edited: Sep 26, 2012
4. Sep 26, 2012

### ImaLooser

Re: Quark-gluon "plasma"

It isn't really frictionless, I think. Close enough for jazz though

5. Sep 27, 2012

### zje2009

Re: Quark-gluon "plasma"

Yes.Lattice is a numerical algorithm of QCD.

6. Sep 27, 2012

### tom.stoer

Re: Quark-gluon "plasma"

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. Sep 27, 2012

### SW VandeCarr

Re: Quark-gluon "plasma"

I'm familiar with the Monte Carlo method. For example, in Monte Carlo integration one has an intractable integral: $I = \int_a^{b} f(x) dx$ which is approximated by:

$\hat I = \frac{b-a}{n} \sum_{i=1}^{n} f(x_{i})$ where $x_i$ 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

Last edited: Sep 27, 2012
8. Sep 27, 2012

### tom.stoer

Re: Quark-gluon "plasma"

In lattice QCD the integral to be evaluated is a so-called path integral