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A Kubos formula for viscosity

  1. Mar 18, 2017 #1
    I am looking for a derivation of the following formula
    \eta=\lim_{\omega\rightarrow0} \frac{1}{2\omega}\int dt dx\langle[T_{xy}(t,x),T_{xy}(0,0)]\rangle,
    where $T_{xy}$ is a component of the stress-energy tensor. This is claimed in for instance https://arxiv.org/pdf/hep-th/0405231.pdf. There seems to be a derivation in https://arxiv.org/pdf/1207.7021.pdf, but it seems overly complicated and involved extra features. So before I dig into that paper to try to understand it, I would like to ask if someone knows a simple derivation of the above Kubo formula for the viscosity?
  2. jcsd
  3. Mar 18, 2017 #2


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    The Kubo formulae are very important. I recommend to first look at the usual many-body approach before using special models like AdS/CFT ;-)). It's linear-response theory. For thermal relativistic QFT you find a nice treatment in

    J. Kapusta, C. Gale, Finite-temperature field theory, Cambridge University Press
  4. Mar 18, 2017 #3
    Actually the paper I referred to just applies the Kubo formula in an AdS/CFT context, but they don't derive it (it just happened to be the place where I saw it). I am interested in a derivation of this formula indeed using standard linear response theory (nothing to do with AdS/CFT). Thanks for the reference, I will have a look.
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