Entanglement used to identify critical systems

We promote use of the geometric entropy formula derived by Holzhey et. al. from conformal field theory, \(S_\ell\sim ({c}/{3}) \log(\sin{\pi\ell}/{N})\), to identify critical regions in zero temperature 1D quantum systems. The method is demonstrated on a class of one-dimensional XY and \(XYZ\) spin-1/2 chains, where the critical regions and their correponding central charges can be reproduced with quite modest computational efforts.