649 research outputs found
Transport Coefficients in Large Gauge Theory: Testing Hard Thermal Loops
We compute shear viscosity and flavor diffusion coefficients for
ultra-relativistic gauge theory with many fermionic species, Nf >> 1, to
leading order in 1/Nf. The calculation is performed both at leading order in
the effective coupling strength g^2 Nf, using the Hard Thermal Loop (HTL)
approximation, and completely to all orders in g^2 Nf. This constitutes a
nontrivial test of how well the HTL approximation works. We find that in this
context, the HTL approximation works well wherever the renormalization point
sensitivity of the leading order HTL result is small.Comment: 31 pages, including 9 figures. Error in vacuum self-energy, arising
from trusting Arthur Weldon, fixed, thank you Tony Rebhan. Results and
conclusions slightly but not significantly change
Transport Coefficients in Hot QCD
I give a physical explanation of what shear viscosity is, and what physics
determines its value. Then I explain why determining the shear viscosity of the
Quark-Gluon Plasma is interesting. I outline the leading-order calculation of
the QGP shear viscosity (and baryon number diffusion constant), explaining why
the quite complicated physics of parton splitting and Landau-Pomeranchuk-Migdal
interference effects are required for its calculation. Then I briefly explore
the range of applicability, emphasizing the importance of plasma instabilities.Comment: 10 pages, invited talk given at the conference "Strong and
Electroweak Matter," Helsinki, Finland 16-19 June 200
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