Holographic c-Function
  We propose a simple and generic holographic $c$-function that is defined purely from geometry by using the non-affine expansion for null congruences. We examined the proposal for BPS black solutions in $\mathcal{N}=2$ gauged supergravity that interpolate between two different dimensional AdS spacetimes and also for domain wall solutions. Moreover, we commented on the relation of this geometric proposal with the one from the holographic entanglement entropy. 
S. Shajidul Haque
hep-th