AdS_7/CFT_6, Gauss-Bonnet Gravity, and Viscosity Bound

Understand

We study the relation between the causality and the positivity of energy bounds in Gauss-Bonnet gravity in AdS_7 background and find a precise agreement.

• Requiring the group velocity of metastable states to be bounded by the speed of light places a bound on the value of Gauss-Bonnet coupling.
• To find the positivity of energy constraints we compute the parameters which determine the angular distribution of the energy flux in terms of three independent coefficients specifying the three-point function of the stress-energy tensor.
• We then relate the latter to the Weyl anomaly of the six-dimensional CFT and compute the anomaly holographically.