How perfect can a gluon plasma be in perturbative QCD?

Journal Article · Tue Feb 01 04:00:00 EST 2011 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.83.034031· OSTI ID:21504891

Chen, Jiunn-Wei ^[1]; Jian, Deng; Hui, Dong ^[2]; Qun, Wang ^[3]

---

1. Department of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan (China)
2. School of Physics, Shandong University, Shandong 250100 (China)
3. Interdisciplinary Center for Theoretical Study and Department of Modern Physics, University of Science and Technology of China, Anhui 230026 (China)

The shear viscosity to entropy density ratio, {eta}/s, characterizes how perfect a fluid is. We calculate the leading order {eta}/s of a gluon plasma in perturbation using the kinetic theory. The leading order contribution only involves the elastic gg{r_reversible}gg (22) process and the inelastic gg{r_reversible}ggg (23) process. The hard-thermal-loop (HTL) treatment is used for the 22 matrix element, while the exact matrix element in vacuum is supplemented by the gluon Debye mass insertion for the 23 process. Also, the asymptotic mass is used for the external gluons in the kinetic theory. The errors from not implementing HTL and the Landau-Pomeranchuk-Migdal effect in the 23 process, and from the uncalculated higher order corrections, are estimated. Our result smoothly connects the two different approximations used by Arnold, Moore, and Yaffe (AMY) and Xu and Greiner (XG). At small {alpha}{sub s} ({alpha}{sub s}<<1), our result is closer to AMY's collinear result while at larger {alpha}{sub s} the finite angle noncollinear configurations become more important and our result is closer to XG's soft bremsstrahlung result. In the region where perturbation is reliable ({alpha}{sub s} < or approx. 0.1), we find no indication that the proposed perfect fluid limit {eta}/s{approx_equal}1/(4{pi}) can be achieved by perturbative QCD alone. Whether this can be achieve for {alpha}{sub s} > or approx. 0.1 is still an open question.

• OSTI ID: 21504891
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 3 Vol. 83; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
APPROXIMATIONS
ASYMPTOTIC SOLUTIONS
BOSONS
BREMSSTRAHLUNG
CALCULATION METHODS
COMPUTERIZED SIMULATION
CONFIGURATION
CORRECTIONS
DENSITY
DISTURBANCES
ELECTROMAGNETIC RADIATION
ENTROPY
FIELD THEORIES
FLUID FLOW
GLUONS
IDEAL FLOW
INCOMPRESSIBLE FLOW
MASS
MATHEMATICAL SOLUTIONS
MATRIX ELEMENTS
PERTURBATION THEORY
PHYSICAL PROPERTIES
PLASMA
QUANTUM CHROMODYNAMICS
QUANTUM FIELD THEORY
RADIATIONS
SIMULATION
STEADY FLOW
THERMODYNAMIC PROPERTIES
VISCOSITY