We use the conformal invariance and the holographic correspondence to fully specify the dependence of entanglement entropy on the extrinsic geometry of the 2d surface $\Sigma$ that separates two subsystems of quantum strongly coupled ${ \mathcal{ N}}=4$ SU(N) superconformal gauge theory. We extend this result and calculate entanglement entropy of a generic 4d conformal field theory. As a byproduct, we obtain a closed-form expression for the entanglement entropy in flat space-time when $\Sigma$ is sphere $S_2$ and when $\Sigma$ is two-dimensional cylinder. The contribution of the type A conformal anomaly to entanglement entropy is always determined by topology of surface $\Sigma$ while the dependence of the entropy on the extrinsic geometry of $\Sigma$ is due to the type B conformal anomaly.
Categories: hep-th cond-mat.stat-mech gr-qc math.DG quant-ph