 
Summary: JHEP02(2004)061
Published by Institute of Physics Publishing for SISSA/ISAS
Received: February 18, 2004
Accepted: February 24, 2004
Shear viscosity in the O(N) model
Gert Aarts and Jose M. Mart´inez Resco
Department of Physics, The Ohio State University
174 West 18th Avenue, Columbus, OH 43210, U.S.A.
Email: aarts@mps.ohiostate.edu, marej@mps.ohiostate.edu
Abstract: We compute the shear viscosity in the O(N) model at first nontrivial order in
the large N expansion. The calculation is organized using the 1/N expansion of the 2PI
effective action (2PI1/N expansion) to nexttoleading order, which leads to an integral
equation summing ladder and bubble diagrams. We also consider the weakly coupled
theory for arbitrary N, using the threeloop expansion of the 2PI effective action. In the
limit of weak coupling and vanishing mass, we find an approximate analytical solution
of the integral equation. For general coupling and mass, the integral equation is solved
numerically using a variational approach. The shear viscosity turns out to be close to the
result obtained in the weakcoupling analysis.
Keywords: 1/N Expansion, Thermal Field Theory.
c SISSA/ISAS 2004 http://jhep.sissa.it/archive/papers/jhep022004061/jhep022004061.pdf
