  Causal holographic information [1] is a variant of the Ryu-Takayanagi
proposal for the entanglement entropy of a spatial region in the context of
AdS/CFT, but with the bulk surface defined by causality rather than
extremality. We investigate the properties of causal holographic information,
focusing in particular on the universal coefficient of the logarithmically
divergent term. We find that this coefficient contains a novel conformal
invariant that cannot be written as an integral of local quantities. By
considering higher curvature corrections in the bulk, we identify the
coefficient of the a and c central charges in 4 dimensions. Finally, we
speculate about which CFT quantity could correspond to the causal holographic
information.
